View Source socket (kernel v9.3)

Socket interface.

This module provides an API for network socket. Functions are provided to create, delete and manipulate the sockets as well as sending and receiving data on them.

The intent is that it shall be as "close as possible" to the OS level socket interface. The only significant addition is that some of the functions, e.g. recv/3, have a time-out argument.

Note

Some functions allow for an asynchronous call. This is achieved by setting the Timeout argument to nowait or to a (select or completion) handle.

For instance, if calling the recv/3 function with Timeout set to nowait (recv(Sock, 0, nowait)) when there is actually nothing to read, it will return with either one of:

CompletionInfo contains the CompletionHandle and SelectInfo contains the SelectHandle.

We have two different implementations. One on Unix (select, based directly on the synchronous standard socket interface) and one on Windows (completion, based on the asynchronous I/O Completion Ports).

These two implementations have a slightly different behaviour and message interface.

The difference will only manifest for the user, if calls are made with the timeout argument set to 'nowait' (see above).

When an completion message is received (with the result of the operation), that means that the operation (connect, send, recv, ...) has been completed (successfully or otherwise). When a select message is received, that only means that the operation can now be completed, via a call to, for instance, connect/1.

The completion message has the format:

  • ____ - {'$socket', socket(), completion, {CompletionHandle, CompletionStatus}}

The select message has the format:

  • ____ - {'$socket', socket(), select, SelectHandle}

Note that, on select "system", all other users are locked out until the 'current user' has called the function (recv for instance) and its return value shows that the operation has completed. Such an operation can also be cancelled with cancel/2.

Instead of Timeout = nowait it is equivalent to create a SelectHandle or CompletionHandle with make_ref() and give as Timeout. This will then be the Handle in the 'completion' or 'select' message, which enables a compiler optimization for receiving a message containing a newly created reference/0 (ignore the part of the message queue that had arrived before the the reference/0 was created).

Another message the user must be prepared for (when making asynchronous calls) is the abort message:

  • ____ - {'$socket', socket(), abort, Info}

This message indicates that the (asynchronous) operation has been aborted. If, for instance, the socket has been closed (by another process), Info will be {SelectHandle, closed}.

Note

The Windows support has currently pre-release status.

Support for IPv6 has been implemented but not fully tested.

SCTP has only been partly implemented (and not tested).

Examples

client(SAddr, SPort) ->
   {ok, Sock} = socket:open(inet, stream, tcp),
   ok = socket:connect(Sock, #{family => inet,
                               addr   => SAddr,
                               port   => SPort}),
   Msg = <<"hello">>,
   ok = socket:send(Sock, Msg),
   ok = socket:shutdown(Sock, write),
   {ok, Msg} = socket:recv(Sock),
   ok = socket:close(Sock).

server(Addr, Port) ->
   {ok, LSock} = socket:open(inet, stream, tcp),
   ok = socket:bind(LSock, #{family => inet,
                             port   => Port,
                             addr   => Addr}),
   ok = socket:listen(LSock),
   {ok, Sock} = socket:accept(LSock),
   {ok, Msg} = socket:recv(Sock),
   ok = socket:send(Sock, Msg),
   ok = socket:close(Sock),
   ok = socket:close(LSock).

Summary

Types

Control messages (ancillary messages) returned by recvmsg/1,2,3,5.

Control messages (ancillary messages) accepted by sendmsg/2,3,4.

A reference/0 that uniquely identifies the (completion) operation, contained in the returned completion_info/0.

Returned by an operation that requires the caller to wait for a completion message containing the CompletionHandle and the result of the operation; the CompletionStatus.

A tag that describes the ongoing (completion) operation (= function name), contained in the returned completion_info/0.

A lowercase atom/0 representing a protocol domain on the platform named AF_* (or PF_*).

Extended Error Info. A term containing additional (error) info if the socket nif has been configured to produce it.

The smallest allowed iov_max value according to POSIX is 16, but check your platform documentation to be sure.

Defines the information elements of the table(s) printed by the i/0, i/1 and i/2 functions.

Corresponds to the C struct ip_mreq for managing multicast groups.

Corresponds to the C struct ip_mreq_source for managing multicast groups.

Corresponds to the C struct ip_msfilter for managing multicast source filtering (RFC 3376).

Lowercase atom/0 values corresponding to the C library constants IP_PMTUDISC_*. Some constant(s) may be unsupported by the platform.

Lowercase atom/0 values corresponding to the C library constants IPTOS_*. Some constant(s) may be unsupported by the platform.

The value default is only valid to set and is translated to the C value -1, meaning the route default.

Corresponds to the C struct ipv6_mreq for managing multicast groups. See also RFC 2553.

Lowercase atom/0 values corresponding to the C library constants IPV6_PMTUDISC_*. Some constant(s) may be unsupported by the platform.

The OS protocol levels for, for example, socket options and control messages, with the following names in the OS header files

Corresponds to the C struct linger for managing the socket option {socket, linger}.

Flags corresponding to the message flag constants on the platform. The flags are lowercase and the constants are uppercase with the prefix MSG_.

Message returned by recvmsg/1,2,3,5.

Message sent by sendmsg/2,3,4.

These are socket options for the otp protocol level, that is {otp, Name} options, above all OS protocol levels. They affect Erlang/OTP's socket implementation.

The POSIX error codes originates from the OS level socket interface.

An atom/0 means any protocol as enumerated by the C library call getprotoent() on the platform, or at least the supported ones of ip | ipv6 | tcp | udp | sctp.

Corresponds to the C struct sctp_assocparams.

Corresponds to the C struct sctp_event_subscribe.

Corresponds to the C struct sctp_initmsg.

Corresponds to the C struct sctp_rtoinfo.

A reference/0 that uniquely identifies the (select) operation, contained in the returned select_info/0.

Returned by an operation that requires the caller to wait for a select message containing the SelectHandle.

A tag that describes the (select) operation (= function name), contained in the returned select_info/0.

The path element will always be a binary when returned from this module. When supplied to an API function in this module it may be a string/0, which will be encoded into a binary according to the native file name encoding on the platform.

As returned by open/1,2,3,4 and accept/1,2.

An opaque socket handle unique for the socket.

Socket option on the form {Level, Opt} where the OS protocol Level = level/0 and Opt is a socket option on that protocol level.

Corresponds to the C struct timeval. The field sec holds seconds, and usec microseconds.

A lowercase atom/0 representing a protocol type on the platform named SOCK_*.

Functions

Bind a name to a socket.

Cancel an asynchronous (select) request.

If MRef is a reference that the calling process obtained by calling monitor/1, this monitor is turned off. If the monitoring is already turned off, nothing happens.

Closes the socket.

This function finalizes a connection setup on a socket, after calling connect(_, _, nowait | select_handle()) that returned {select, SelectInfo}, and receiving the select message {'$socket', Socket, select, SelectHandle}, and returns whether the connection setup was successful or not.

Gets a socket option from the protocol level otp, which is this implementation's level above the OS protocol layers.

getopt(Socket, Level, Opt) -> ok | {error, Reason}

Gets a socket option that may be unknown to our implementation, or that has a type not compatible with our implementation, that is; in "native mode".

i()

Print all sockets in table format in the erlang shell.

i/1

Print all sockets in table format in the erlang shell. What information is included is defined by InfoKeys.

i/2

Print a selection, based on domain, of the sockets in table format in the erlang shell. What information is included is defined by InfoKeys.

Get miscellaneous info about the socket library.

Get miscellaneous info about the socket.

Retrieve socket (device) parameters.

Set socket (device) parameters. This function sets a specific parameter, according to SetRequest argument. The third argument is the "key", identifying the interface (usually the name of the interface), and the fourth is the "new" value.

This function retrieves information about what the platform supports, such as if SCTP is supported, or if a socket options are supported.

Equivalent to listen/2

Listen for connections on a socket.

Start monitor the socket Socket.

Returns the number of active sockets.

Equivalent to open/2

Creates an endpoint (socket) for communication based on an already existing file descriptor. The function attempts to retrieve domain, type and protocol from the system. This is however not possible on all platforms, and they should then be specified in Opts.

Creates an endpoint (socket) for communication.

Creates an endpoint (socket) for communication.

Returns the address of the peer connected to the socket.

Equivalent to recv/4

Equivalent to recv/4

Equivalent to recv/4

Equivalent to recvfrom/4

Equivalent to recvfrom/4

Equivalent to recvmsg/5

Equivalent to recvmsg/5

Equivalent to recvmsg/5

Equivalent to send/4

Equivalent to send/4

sendfile(Socket, FileHandle) -> Result

Depending on the Timeout argument; the same as sendfile(Socket, FileHandle, 0, 0, infinity), sendfile(Socket, FileHandle, 0, 0, Timeout), or sendfile(Socket, FileHandle, 0, 0, SelectHandle), that is: send all data in the file to the socket, with the given Timeout.

The same as sendfile(Socket, FileHandle, Offset, Count, infinity), that is: send the file data at Offset and Count to the socket, without time-out other than from the platform's network stack.

Equivalent to sendmsg/4

Sets a socket option in the protocol level otp, which is this implementation's level above the OS protocol layers.

setopt(Socket, Level, Opt, Value) -> ok | {error, Reason}

Sets a socket option that may be unknown to our implementation, or that has a type not compatible with our implementation, that is; in "native mode".

Shut down all or part of a full-duplex connection.

Returns the current address to which the socket is bound.

Equivalent to supports/2

Equivalent to supports/2

These functions function retrieves information about what the platform supports, such which platform features or which socket options, are supported.

Globally change if the socket registry is to be used or not. Note that its still possible to override this explicitly when creating an individual sockets, see open/2 or open/4 for more info (use the Extra argument).

Returns a list of all sockets, according to the filter rule.

Types

Link to this type

cmsg()

View Source (since OTP 22.0)
-type cmsg() :: cmsg_recv() | cmsg_send().
Link to this type

cmsg_recv()

View Source (since OTP 22.0)
-type cmsg_recv() ::
    #{level := socket, type := timestamp, data := binary(), value => timeval()} |
    #{level := socket, type := rights, data := binary()} |
    #{level := socket, type := credentials, data := binary()} |
    #{level := ip, type := tos, data := binary(), value => ip_tos() | integer()} |
    #{level := ip, type := recvtos, data := binary(), value := ip_tos() | integer()} |
    #{level := ip, type := ttl, data := binary(), value => integer()} |
    #{level := ip, type := recvttl, data := binary(), value := integer()} |
    #{level := ip, type := pktinfo, data := binary(), value => ip_pktinfo()} |
    #{level := ip, type := origdstaddr, data := binary(), value => sockaddr_recv()} |
    #{level := ip, type := recverr, data := binary(), value => extended_err()} |
    #{level := ipv6, type := hoplimit, data := binary(), value => integer()} |
    #{level := ipv6, type := pktinfo, data := binary(), value => ipv6_pktinfo()} |
    #{level := ipv6, type := recverr, data := binary(), value => extended_err()} |
    #{level := ipv6, type := tclass, data := binary(), value => integer()}.

Control messages (ancillary messages) returned by recvmsg/1,2,3,5.

A control message has got a data field with a native (binary) value for the message data, and may also have a decoded value field if this socket library successfully decoded the data.

Link to this type

cmsg_send()

View Source (since OTP 22.0)
-type cmsg_send() ::
    #{level := socket, type := timestamp, data => native_value(), value => timeval()} |
    #{level := socket, type := rights, data := native_value()} |
    #{level := socket, type := credentials, data := native_value()} |
    #{level := ip, type := tos, data => native_value(), value => ip_tos() | integer()} |
    #{level := ip, type := ttl, data => native_value(), value => integer()} |
    #{level := ip, type := hoplimit, data => native_value(), value => integer()} |
    #{level := ipv6, type := tclass, data => native_value(), value => integer()}.

Control messages (ancillary messages) accepted by sendmsg/2,3,4.

A control message may for some message types have a value field with a symbolic value, or a data field with a native value, that has to be binary compatible what is defined in the platform's header files.

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completion_handle()

View Source (since OTP 22.0)
-type completion_handle() :: reference().

A reference/0 that uniquely identifies the (completion) operation, contained in the returned completion_info/0.

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completion_info()

View Source (since OTP 22.0)
-type completion_info() ::
    {completion_info, CompletionTag :: completion_tag(), CompletionHandle :: completion_handle()}.

Returned by an operation that requires the caller to wait for a completion message containing the CompletionHandle and the result of the operation; the CompletionStatus.

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completion_tag()

View Source (since OTP 22.0)
-type completion_tag() :: accept | connect | recv | recvfrom | recvmsg | send | sendto | sendmsg.

A tag that describes the ongoing (completion) operation (= function name), contained in the returned completion_info/0.

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domain()

View Source (since OTP 22.0)
-type domain() :: inet | inet6 | local | unspec.

A lowercase atom/0 representing a protocol domain on the platform named AF_* (or PF_*).

The calls supports(), is_supported(ipv6) and is_supported(local) tells if the IPv6 protocol for the inet6 protocol domain / address family, and if the local protocol domain / address family is supported by the platform's header files.

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ee_origin()

View Source (since OTP 22.0)
-type ee_origin() :: none | local | icmp | icmp6.
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eei()

View Source (since OTP 22.0)
-type eei() ::
    #{info := econnreset | econnaborted | netname_deleted | too_many_cmds | atom(),
      raw_info := term()}.

Extended Error Info. A term containing additional (error) info if the socket nif has been configured to produce it.

Link to this type

extended_err()

View Source (since OTP 22.0)
-type extended_err() ::
    #{error := posix(),
      origin := icmp,
      type := dest_unreach,
      code := icmp_dest_unreach() | 0..255,
      info := 0..4294967295,
      data := 0..4294967295,
      offender := sockaddr_recv()} |
    #{error := posix(),
      origin := icmp,
      type := time_exceeded | 0..255,
      code := 0..255,
      info := 0..4294967295,
      data := 0..4294967295,
      offender := sockaddr_recv()} |
    #{error := posix(),
      origin := icmp6,
      type := dest_unreach,
      code := icmpv6_dest_unreach() | 0..255,
      info := 0..4294967295,
      data := 0..4294967295,
      offender := sockaddr_recv()} |
    #{error := posix(),
      origin := icmp6,
      type := pkt_toobig | time_exceeded | 0..255,
      code := 0..255,
      info := 0..4294967295,
      data := 0..4294967295,
      offender := sockaddr_recv()} |
    #{error := posix(),
      origin := ee_origin() | 0..255,
      type := 0..255,
      code := 0..255,
      info := 0..4294967295,
      data := 0..4294967295,
      offender := sockaddr_recv()}.
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hatype()

View Source (not exported) (since OTP 22.0)
-type hatype() ::
    netrom | eether | ether | ax25 | pronet | chaos | ieee802 | arcnet | appletlk | dlci | atm |
    metricom | ieee1394 | eui64 | infiniband | tunnel | tunnel6 | loopback | localtlk | none |
    void |
    non_neg_integer().
Link to this type

icmp_dest_unreach()

View Source (since OTP 22.0)
-type icmp_dest_unreach() ::
    net_unreach | host_unreach | port_unreach | frag_needed | net_unknown | host_unknown.
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icmpv6_dest_unreach()

View Source (since OTP 22.0)
-type icmpv6_dest_unreach() ::
    noroute | adm_prohibited | not_neighbour | addr_unreach | port_unreach | policy_fail |
    reject_route.
Link to this type

in6_addr()

View Source (since OTP 22.0)
-type in6_addr() :: {0..65535, 0..65535, 0..65535, 0..65535, 0..65535, 0..65535, 0..65535, 0..65535}.
Link to this type

in6_flow_info()

View Source (not exported) (since OTP 22.0)
-type in6_flow_info() :: 0..1048575.
Link to this type

in6_scope_id()

View Source (not exported) (since OTP 22.0)
-type in6_scope_id() :: 0..4294967295.
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in_addr()

View Source (since OTP 22.0)
-type in_addr() :: {0..255, 0..255, 0..255, 0..255}.
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info()

View Source (not exported) (since OTP 22.0)
-type info() ::
    #{counters := #{atom() := non_neg_integer()},
      iov_max := non_neg_integer(),
      use_registry := boolean(),
      io_backend := #{name := atom()}}.

The smallest allowed iov_max value according to POSIX is 16, but check your platform documentation to be sure.

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info_keys()

View Source (since OTP 22.0)
-type info_keys() ::
    [domain | type | protocol | fd | owner | local_address | remote_address | recv | sent | state].

Defines the information elements of the table(s) printed by the i/0, i/1 and i/2 functions.

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invalid()

View Source (since OTP 22.0)
-type invalid() :: {invalid, What :: term()}.
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ioctl_device_flag()

View Source (since OTP 22.0)
-type ioctl_device_flag() ::
    up | broadcast | debug | loopback | pointopoint | notrailers | knowsepoch | running | noarp |
    promisc | allmulti | master | oactive | slave | simplex | link0 | link1 | link2 | multicast |
    portsel | automedia | cantconfig | ppromisc | dynamic | monitor | staticarp | dying |
    renaming | nogroup | lower_up | dormant | echo.
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ioctl_device_map()

View Source (since OTP 22.0)
-type ioctl_device_map() ::
    #{mem_start := non_neg_integer(),
      mem_end := non_neg_integer(),
      base_addr := non_neg_integer(),
      irq := non_neg_integer(),
      dma := non_neg_integer(),
      port := non_neg_integer()}.
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ip_mreq()

View Source (since OTP 22.0)
-type ip_mreq() :: #{multiaddr := in_addr(), interface := in_addr()}.

Corresponds to the C struct ip_mreq for managing multicast groups.

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ip_mreq_source()

View Source (since OTP 22.0)
-type ip_mreq_source() :: #{multiaddr := in_addr(), interface := in_addr(), sourceaddr := in_addr()}.

Corresponds to the C struct ip_mreq_source for managing multicast groups.

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ip_msfilter()

View Source (since OTP 22.0)
-type ip_msfilter() ::
    #{multiaddr := in_addr(),
      interface := in_addr(),
      mode := include | exclude,
      slist := [in_addr()]}.

Corresponds to the C struct ip_msfilter for managing multicast source filtering (RFC 3376).

Link to this type

ip_pktinfo()

View Source (since OTP 22.0)
-type ip_pktinfo() :: #{ifindex := non_neg_integer(), spec_dst := in_addr(), addr := in_addr()}.
Link to this type

ip_pmtudisc()

View Source (since OTP 22.0)
-type ip_pmtudisc() :: want | dont | do | probe.

Lowercase atom/0 values corresponding to the C library constants IP_PMTUDISC_*. Some constant(s) may be unsupported by the platform.

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ip_tos()

View Source (since OTP 22.0)
-type ip_tos() :: lowdelay | throughput | reliability | mincost.

Lowercase atom/0 values corresponding to the C library constants IPTOS_*. Some constant(s) may be unsupported by the platform.

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ipv6_hops()

View Source (since OTP 22.0)
-type ipv6_hops() :: default | 0..255.

The value default is only valid to set and is translated to the C value -1, meaning the route default.

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ipv6_mreq()

View Source (since OTP 22.0)
-type ipv6_mreq() :: #{multiaddr := in6_addr(), interface := non_neg_integer()}.

Corresponds to the C struct ipv6_mreq for managing multicast groups. See also RFC 2553.

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ipv6_pktinfo()

View Source (since OTP 22.0)
-type ipv6_pktinfo() :: #{addr := in6_addr(), ifindex := integer()}.
Link to this type

ipv6_pmtudisc()

View Source (since OTP 22.0)
-type ipv6_pmtudisc() :: want | dont | do | probe.

Lowercase atom/0 values corresponding to the C library constants IPV6_PMTUDISC_*. Some constant(s) may be unsupported by the platform.

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level()

View Source (since OTP 22.0)
-type level() :: socket | protocol().

The OS protocol levels for, for example, socket options and control messages, with the following names in the OS header files:

  • socket - SOL_SOCKET with options named SO_*.

  • ip - IPPROTO_IP a.k.a SOL_IP with options named IP_*.

  • ipv6 - IPPROTO_IPV6 a.k.a SOL_IPV6 with options named IPV6_*.

  • tcp - IPPROTO_TCP with options named TCP_*.

  • udp - IPPROTO_UDP with options named UDP_*.

  • sctp - IPPROTO_SCTP with options named SCTP_*.

There are many other possible protocols, but the ones above are those for which this socket library implements socket options and/or control messages.

All protocols known to the OS are enumerated when the Erlang VM is started. See the OS man page for protocols(5). The protocol level 'socket' is always implemented as SOL_SOCKET and all the others mentioned in the list above are valid, if supported by the platform, enumerated or not.

The calls supports() and is_supported(protocols, Protocol) can be used to find out if protocols ipv6 and/or sctp are supported according to the platform's header files.

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linger()

View Source (since OTP 22.0)
-type linger() :: #{onoff := boolean(), linger := non_neg_integer()}.

Corresponds to the C struct linger for managing the socket option {socket, linger}.

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msg()

View Source (since OTP 22.0)
-type msg() :: msg_send() | msg_recv().
Link to this type

msg_flag()

View Source (since OTP 22.0)
-type msg_flag() ::
    cmsg_cloexec | confirm | ctrunc | dontroute | eor | errqueue | more | oob | peek | trunc.

Flags corresponding to the message flag constants on the platform. The flags are lowercase and the constants are uppercase with the prefix MSG_.

Some flags are only used for sending, some only for receiving, some in received control messages, and some for several of these. Not all flags are supported on all platforms. See the platform's documentation, supports(msg_flags), and is_supported(msg_flags, MsgFlag).

Link to this type

msg_recv()

View Source (since OTP 22.0)
-type msg_recv() ::
    #{addr => sockaddr_recv(),
      iov := erlang:iovec(),
      ctrl := [cmsg_recv() | #{level := level() | integer(), type := integer(), data := binary()}],
      flags := [msg_flag() | integer()]}.

Message returned by recvmsg/1,2,3,5.

Corresponds to a C struct msghdr, see your platform documentation for recvmsg(2).

  • addr - Optional peer address, used on unconnected sockets. Corresponds to msg_name and msg_namelen fields of a struct msghdr. If NULL the map key is not present.

  • iov - Data as a list of binaries. The msg_iov and msg_iovlen fields of a struct msghdr.

  • ctrl - A possibly empty list of control messages (CMSG). Corresponds to the msg_control and msg_controllen fields of a struct msghdr.

  • flags - Message flags. Corresponds to the msg_flags field of a struct msghdr. Unknown flags, if any, are returned in one integer/0, last in the containing list.

Link to this type

msg_send()

View Source (since OTP 22.0)
-type msg_send() ::
    #{addr => sockaddr(),
      iov := erlang:iovec(),
      ctrl => [cmsg_send() | #{level := level() | integer(), type := integer(), data := binary()}]}.

Message sent by sendmsg/2,3,4.

Corresponds to a C struct msghdr, see your platform documentation for sendmsg(2).

  • addr - Optional peer address, used on unconnected sockets. Corresponds to msg_name and msg_namelen fields of a struct msghdr. If not used they are set to NULL, 0.

  • iov - Mandatory data as a list of binaries. The msg_iov and msg_iovlen fields of a struct msghdr.

  • ctrl - Optional list of control messages (CMSG). Corresponds to the msg_control and msg_controllen fields of a struct msghdr. If not used they are set to NULL, 0.

The msg_flags field of the struct msghdr is set to 0.

Link to this type

native_value()

View Source (not exported) (since OTP 22.0)
-type native_value() :: integer() | boolean() | binary().
Link to this type

otp_socket_option()

View Source (since OTP 22.0)
-type otp_socket_option() ::
    debug | iow | controlling_process | rcvbuf | rcvctrlbuf | sndctrlbuf | meta | use_registry |
    fd | domain.

These are socket options for the otp protocol level, that is {otp, Name} options, above all OS protocol levels. They affect Erlang/OTP's socket implementation.

  • debug - boolean/0 - Activate debug printout.

  • iow - boolean/0 - Inform On Wrap of statistics counters.

  • controlling_process - pid/0 - The socket "owner". Only the current controlling process can set this option.

  • rcvbuf - BufSize :: (default | integer()>0) | {N :: integer()>0, BufSize :: (default | integer()>0)}- Receive buffer size.

    The value default is only valid to set.

    N specifies the number of read attempts to do in a tight loop before assuming no more data is pending.

    This is the allocation size for the receive buffer used when calling the OS protocol stack's receive API, when no specific size (size 0) is requested. When the receive function returns the receive buffer is reallocated to the actually received size. If the data is copied or shrinked in place is up to the allocator, and can to some extent be configured in the Erlang VM.

    The similar socket option; {socket,rcvbuf} is a related option for the OS' protocol stack that on Unix corresponds to SOL_SOCKET,SO_RCVBUF.

  • rcvctrlbuf - BufSize :: (default | integer()>0)- Allocation size for the ancillary data buffer used when calling the OS protocol stack's receive API.

    The value default is only valid to set.

  • sndctrlbuf - BufSize :: (default | integer()>0)- Allocation size for the ancillary data buffer used when calling the OS protocol stack's sendmsg API.

    The value default is only valid to set.

    It is the user's responsibility to set a buffer size that has room for the encoded ancillary data in the message to send.

    See sendmsg and also the ctrl field of the msg_send/0 type.

  • fd - integer/0 - Only valid to get. The OS protocol levels' socket descriptor. Functions open/1,2 can be used to create a socket according to this module from an existing OS socket descriptor.

  • use_registry - boolean/0 - Only valid to get. The value is set when the socket is created with open/2 or open/4.

Options not described here are intentionally undocumented and for Erlang/OTP internal use only.

Link to this type

packet_type()

View Source (not exported) (since OTP 22.0)
-type packet_type() ::
    host | broadcast | multicast | otherhost | outgoing | loopback | user | kernel | fastroute |
    non_neg_integer().
Link to this type

port_number()

View Source (since OTP 22.0)
-type port_number() :: 0..65535.
Link to this type

posix()

View Source (not exported) (since OTP 22.0)
-type posix() :: inet:posix().

The POSIX error codes originates from the OS level socket interface.

Link to this type

protocol()

View Source (since OTP 22.0)
-type protocol() :: atom().

An atom/0 means any protocol as enumerated by the C library call getprotoent() on the platform, or at least the supported ones of ip | ipv6 | tcp | udp | sctp.

See open/2,3,4

The call supports(protocols) returns which protocols are supported, and is_supported(protocols, Protocol) tells if Protocol is among the enumerated.

Link to this type

sctp_assocparams()

View Source (since OTP 22.0)
-type sctp_assocparams() ::
    #{assoc_id := integer(),
      asocmaxrxt := 0..65535,
      numbe_peer_destinations := 0..65535,
      peer_rwnd := 0..4294967295,
      local_rwnd := 0..4294967295,
      cookie_life := 0..4294967295}.

Corresponds to the C struct sctp_assocparams.

Link to this type

sctp_event_subscribe()

View Source (since OTP 22.0)
-type sctp_event_subscribe() ::
    #{data_io := boolean(),
      association := boolean(),
      address := boolean(),
      send_failure := boolean(),
      peer_error := boolean(),
      shutdown := boolean(),
      partial_delivery := boolean(),
      adaptation_layer => boolean(),
      sender_dry => boolean()}.

Corresponds to the C struct sctp_event_subscribe.

Not all fields are implemented on all platforms; unimplemented fields are ignored, but implemented fields are mandatory. Note that the '_event' suffixes have been stripped from the C struct field names, for convenience.

Link to this type

sctp_initmsg()

View Source (since OTP 22.0)
-type sctp_initmsg() ::
    #{num_ostreams := 0..65535,
      max_instreams := 0..65535,
      max_attempts := 0..65535,
      max_init_timeo := 0..65535}.

Corresponds to the C struct sctp_initmsg.

Link to this type

sctp_rtoinfo()

View Source (since OTP 22.0)
-type sctp_rtoinfo() ::
    #{assoc_id := integer(), initial := 0..4294967295, max := 0..4294967295, min := 0..4294967295}.

Corresponds to the C struct sctp_rtoinfo.

Link to this type

select_handle()

View Source (since OTP 22.0)
-type select_handle() :: reference().

A reference/0 that uniquely identifies the (select) operation, contained in the returned select_info/0.

Link to this type

select_info()

View Source (since OTP 22.0)
-type select_info() :: {select_info, SelectTag :: select_tag(), SelectHandle :: select_handle()}.

Returned by an operation that requires the caller to wait for a select message containing the SelectHandle.

Link to this type

select_tag()

View Source (since OTP 22.0)
-type select_tag() ::
    accept | connect | recv | recvfrom | recvmsg | send | sendto | sendmsg |
    sendfile |
    {recv | recvfrom | recvmsg | send | sendto | sendmsg | sendfile, ContData :: term()}.

A tag that describes the (select) operation (= function name), contained in the returned select_info/0.

Link to this type

sockaddr()

View Source (since OTP 22.0)
Link to this type

sockaddr_dl()

View Source (since OTP 22.0)
-type sockaddr_dl() ::
    #{family := link,
      index := non_neg_integer(),
      type := non_neg_integer(),
      nlen := non_neg_integer(),
      alen := non_neg_integer(),
      slen := non_neg_integer(),
      data := binary()}.
Link to this type

sockaddr_in6()

View Source (since OTP 22.0)
-type sockaddr_in6() ::
    #{family := inet6,
      port := port_number(),
      addr := any | loopback | in6_addr(),
      flowinfo := in6_flow_info(),
      scope_id := in6_scope_id()}.
Link to this type

sockaddr_in()

View Source (since OTP 22.0)
-type sockaddr_in() ::
    #{family := inet, port := port_number(), addr := any | broadcast | loopback | in_addr()}.
Link to this type

sockaddr_ll()

View Source (since OTP 22.0)
-type sockaddr_ll() ::
    #{family := packet,
      protocol := non_neg_integer(),
      ifindex := integer(),
      pkttype := packet_type(),
      hatype := hatype(),
      addr := binary()}.
Link to this type

sockaddr_native()

View Source (since OTP 22.0)
-type sockaddr_native() :: #{family := integer(), addr := binary()}.
Link to this type

sockaddr_recv()

View Source (since OTP 22.0)
-type sockaddr_recv() :: sockaddr() | binary().
Link to this type

sockaddr_un()

View Source (since OTP 22.0)
-type sockaddr_un() :: #{family := local, path := binary() | string()}.

The path element will always be a binary when returned from this module. When supplied to an API function in this module it may be a string/0, which will be encoded into a binary according to the native file name encoding on the platform.

A terminating zero character will be appended before the address path is given to the OS, and the terminating zero will be stripped before giving the address path to the caller.

Linux's non-portable abstract socket address extension is handled by not doing any terminating zero processing in either direction, if the first byte of the address is zero.

Link to this type

sockaddr_unspec()

View Source (since OTP 22.0)
-type sockaddr_unspec() :: #{family := unspec, addr := binary()}.
Link to this type

socket()

View Source (since OTP 22.0)
-type socket() :: {'$socket', socket_handle()}.

As returned by open/1,2,3,4 and accept/1,2.

Link to this type

socket_counters()

View Source (since OTP 22.0)
-type socket_counters() ::
    #{read_byte := non_neg_integer(),
      read_fails := non_neg_integer(),
      read_pkg := non_neg_integer(),
      read_pkg_max := non_neg_integer(),
      read_tries := non_neg_integer(),
      read_waits := non_neg_integer(),
      write_byte := non_neg_integer(),
      write_fails := non_neg_integer(),
      write_pkg := non_neg_integer(),
      write_pkg_max := non_neg_integer(),
      write_tries := non_neg_integer(),
      write_waits := non_neg_integer(),
      sendfile => non_neg_integer(),
      sendfile_byte => non_neg_integer(),
      sendfile_fails => non_neg_integer(),
      sendfile_max => non_neg_integer(),
      sendfile_pkg => non_neg_integer(),
      sendfile_pkg_max => non_neg_integer(),
      sendfile_tries => non_neg_integer(),
      sendfile_waits => non_neg_integer(),
      acc_success := non_neg_integer(),
      acc_fails := non_neg_integer(),
      acc_tries := non_neg_integer(),
      acc_waits := non_neg_integer()}.
Link to this opaque

socket_handle()

View Source (opaque) (since OTP 22.0)
-opaque socket_handle()

An opaque socket handle unique for the socket.

Link to this type

socket_info()

View Source (since OTP 22.0)
-type socket_info() ::
    #{domain := domain() | integer(),
      type := type() | integer(),
      protocol := protocol() | integer(),
      owner := pid(),
      ctype := normal | fromfd | {fromfd, integer()},
      counters := socket_counters(),
      num_readers := non_neg_integer(),
      num_writers := non_neg_integer(),
      num_acceptors := non_neg_integer(),
      writable := boolean(),
      readable := boolean(),
      rstates := [atom()],
      wstates := [atom()]}.
Link to this type

socket_option()

View Source (since OTP 22.0)
-type socket_option() ::
    {Level :: socket,
     Opt ::
         acceptconn | acceptfilter | bindtodevice | broadcast | bsp_state | busy_poll | debug |
         domain | dontroute | error | exclusiveaddruse | keepalive | linger | mark | maxdg |
         max_msg_size | oobinline | passcred | peek_off | peercred | priority | protocol |
         rcvbuf | rcvbufforce | rcvlowat | rcvtimeo | reuseaddr | reuseport | rxq_ovfl | setfib |
         sndbuf | sndbufforce | sndlowat | sndtimeo | timestamp | type} |
    {Level :: ip,
     Opt ::
         add_membership | add_source_membership | block_source | dontfrag | drop_membership |
         drop_source_membership | freebind | hdrincl | minttl | msfilter | mtu | mtu_discover |
         multicast_all | multicast_if | multicast_loop | multicast_ttl | nodefrag | options |
         pktinfo | recvdstaddr | recverr | recvif | recvopts | recvorigdstaddr | recvtos |
         recvttl | retopts | router_alert | sndsrcaddr | tos | transparent | ttl | unblock_source} |
    {Level :: ipv6,
     Opt ::
         addrform | add_membership | authhdr | auth_level | checksum | drop_membership | dstopts |
         esp_trans_level | esp_network_level | faith | flowinfo | hopopts | ipcomp_level |
         join_group | leave_group | mtu | mtu_discover | multicast_hops | multicast_if |
         multicast_loop | portrange | pktoptions | recverr | recvhoplimit | hoplimit |
         recvpktinfo | pktinfo | recvtclass | router_alert | rthdr | tclass | unicast_hops |
         use_min_mtu | v6only} |
    {Level :: tcp,
     Opt ::
         congestion | cork | info | keepcnt | keepidle | keepintvl | maxseg | md5sig | nodelay |
         noopt | nopush | syncnt | user_timeout} |
    {Level :: udp, Opt :: cork} |
    {Level :: sctp,
     Opt ::
         adaption_layer | associnfo | auth_active_key | auth_asconf | auth_chunk | auth_key |
         auth_delete_key | autoclose | context | default_send_params | delayed_ack_time |
         disable_fragments | hmac_ident | events | explicit_eor | fragment_interleave |
         get_peer_addr_info | initmsg | i_want_mapped_v4_addr | local_auth_chunks | maxseg |
         maxburst | nodelay | partial_delivery_point | peer_addr_params | peer_auth_chunks |
         primary_addr | reset_streams | rtoinfo | set_peer_primary_addr | status |
         use_ext_recvinfo}.

Socket option on the form {Level, Opt} where the OS protocol Level = level/0 and Opt is a socket option on that protocol level.

The OS name for an options is, except where otherwise noted, the Opt atom, in capitals, with prefix according to level/0.

Note

The IPv6 option pktoptions is a special (barf) case. It is intended for backward compatibility usage only.

Do not use this option.

Note

See the OS documentation for every socket option.

An option below that has the value type boolean/0 will translate the value false to a C int with value 0, and the value true to !!0 (not (not false)).

An option with value type integer/0 will be translated to a C int that may have a restricted range, for example byte: 0..255. See the OS documentation.

The calls supports(options), supports(options, Level) and is_supported(options, {Level, Opt}) can be used to find out which socket options that are supported by the platform.

Options for protocol level socket:

  • {socket, acceptconn} - Value = boolean()

  • {socket, bindtodevice} - Value = string()

  • {socket, broadcast} - Value = boolean()

  • {socket, debug} - Value = integer()

  • {socket, domain} - Value = domain/0

    Only valid to get.

    The socket's protocol domain. Does not work on for instance FreeBSD.

  • {socket, dontroute} - Value = boolean()

  • {socket, keepalive} - Value = boolean()

  • {socket, linger} - Value = abort | linger/0

    The value abort is shorthand for #{onoff => true, linger => 0}, and only valid to set.

  • {socket, oobinline} - Value = boolean()

  • {socket, passcred} - Value = boolean()

  • {socket, peek_off} - Value = integer()

    Currently disabled due to a possible infinite loop when calling recv/1-4 with peek in Flags.

  • {socket, priority} - Value = integer()

  • {socket, protocol} - Value = protocol/0

    Only valid to get.

    The socket's protocol. Does not work on for instance Darwin.

  • {socket, rcvbuf} - Value = integer()

  • {socket, rcvlowat} - Value = integer()

  • {socket, rcvtimeo} - Value = timeval/0

    This option is unsupported per default; OTP has to be explicitly built with the --enable-esock-rcvsndtimeo configure option for this to be available.

    Since our implementation uses nonblocking sockets, it is unknown if and how this option works, or even if it may cause malfunction. Therefore, we do not recommend setting this option.

    Instead, use the Timeout argument to, for instance, the recv/3 function.

  • {socket, reuseaddr} - Value = boolean()

  • {socket, reuseport} - Value = boolean()

  • {socket, sndbuf} - Value = integer()

  • {socket, sndlowat} - Value = integer()

  • {socket, sndtimeo} - Value = timeval/0

    This option is unsupported per default; OTP has to be explicitly built with the --enable-esock-rcvsndtimeo configure option for this to be available.

    Since our implementation uses nonblocking sockets, it is unknown if and how this option works, or even if it may cause malfunction. Therefore, we do not recommend setting this option.

    Instead, use the Timeout argument to, for instance, the send/3 function.

  • {socket, timestamp} - Value = boolean()

  • {socket, type} - Value = type/0

    Only valid to get.

    The socket's type.

Options for protocol level ip:

  • {ip, add_membership} - Value = ip_mreq/0

    Only valid to set.

  • {ip, add_source_membership} - Value = ip_mreq_source/0

    Only valid to set.

  • {ip, block_source} - Value = ip_mreq_source/0

    Only valid to set.

  • {ip, drop_membership} - Value = ip_mreq/0

    Only valid to set.

  • {ip, drop_source_membership} - Value = ip_mreq_source/0

    Only valid to set.

  • {ip, freebind} - Value = boolean()

  • {ip, hdrincl} - Value = boolean()

  • {ip, minttl} - Value = integer()

  • {ip, msfilter} - Value = null | ip_msfilter/0

    Only valid to set.

    The value null passes a NULL pointer and size 0 to the C library call.

  • {ip, mtu} - Value = integer()

    Only valid to get.

  • {ip, mtu_discover} - Value = ip_pmtudisc() | integer()

    An integer/0 value is according to the platform's header files.

  • {ip, multicast_all} - Value = boolean()

  • {ip, multicast_if} - Value = any | in_addr/0

  • {ip, multicast_loop} - Value = boolean()

  • {ip, multicast_ttl} - Value = integer()

  • {ip, nodefrag} - Value = boolean()

  • {ip, pktinfo} - Value = boolean()

  • {ip, recvdstaddr} - Value = boolean()

  • {ip, recverr} - Value = boolean()

    Warning! When this option is enabled, error messages may arrive on the socket's error queue, which should be read using the message flag errqueue, and using recvmsg/1,2,3,4,5 to get all error information in the message's ctrl field as a control message #{level := ip, type := recverr}.

    A working strategy should be to first poll the error queue using recvmsg/2,3,4 with Timeout =:= 0 and Flags containing errqueue (ignore the return value {error, timeout}) before reading the actual data to ensure that the error queue gets cleared. And read the data using one of the nowait | select_handle() recv functions: recv/3,4, recvfrom/3,4 or recvmsg/3,4,5. Otherwise you might accidentally cause a busy loop in and out of 'select' for the socket.

  • {ip, recvif} - Value = boolean()

  • {ip, recvopts} - Value = boolean()

  • {ip, recvorigdstaddr} - Value = boolean()

  • {ip, recvtos} - Value = boolean()

  • {ip, recvttl} - Value = boolean()

  • {ip, retopts} - Value = boolean()

  • {ip, router_alert} - Value = integer()

  • {ip, sendsrcaddr} - Value = boolean()

  • {ip, tos} - Value = ip_tos() | integer()

    An integer/0 value is according to the platform's header files.

  • {ip, transparent} - Value = boolean()

  • {ip, ttl} - Value = integer()

  • {ip, unblock_source} - Value = ip_mreq_source/0

    Only valid to set.

Options for protocol level ipv6:

  • {ipv6, addrform} - Value = domain/0

    As far as we know the only valid value is inet and it is only allowed for an IPv6 socket that is connected and bound to an IPv4-mapped IPv6 address.

  • {ipv6, add_membership} - Value = ipv6_mreq/0

    Only valid to set.

  • {ipv6, authhdr} - Value = boolean()

  • {ipv6, drop_membership} - Value = ipv6_mreq/0

    Only valid to set.

  • {ipv6, dstopts} - Value = boolean()

  • {ipv6, flowinfo} - Value = boolean()

  • {ipv6, hoplimit} - Value = boolean()

  • {ipv6, hopopts} - Value = boolean()

  • {ipv6, mtu} - Value = integer()

  • {ipv6, mtu_discover} - Value = ipv6_pmtudisc() | integer()

    An integer/0 value is according to the platform's header files.

  • {ipv6, multicast_hops} - Value = ipv6_hops/0

  • {ipv6, multicast_if} - Value = integer()

  • {ipv6, multicast_loop} - Value = boolean()

  • {ipv6, recverr} - Value = boolean()

    Warning! See the socket option {ip, recverr} regarding the socket's error queue. The same warning applies for this option.

  • {ipv6, recvhoplimit} - Value = boolean()

  • {ipv6, recvpktinfo} - Value = boolean()

  • {ipv6, recvtclass} - Value = boolean()

  • {ipv6, router_alert} - Value = integer()

  • {ipv6, rthdr} - Value = boolean()

  • {ipv6, tclass} - Value = boolean()

  • {ipv6, unicast_hops} - Value = ipv6_hops/0

  • {ipv6, v6only} - Value = boolean()

Options for protocol level sctp. See also RFC 6458.

  • {sctp, associnfo} - Value = sctp_assocparams/0

  • {sctp, autoclose} - Value = integer()

  • {sctp, disable_fragments} - Value = boolean()

  • {sctp, events} - Value = sctp_event_subscribe/0

    Only valid to set.

  • {sctp, initmsg} - Value = sctp_initmsg/0

  • {sctp, maxseg} - Value = integer()

  • {sctp, nodelay} - Value = boolean()

  • {sctp, rtoinfo} - Value = sctp_rtoinfo/0

Options for protocol level tcp:

  • {tcp, congestion} - Value = string()

  • {tcp, cork} - Value = boolean()

  • {tcp, maxseg} - Value = integer()

  • {tcp, nodelay} - Value = boolean()

Options for protocol level udp:

  • {udp, cork} - Value = boolean()
Link to this type

timeval()

View Source (since OTP 22.0)
-type timeval() :: #{sec := integer(), usec := integer()}.

Corresponds to the C struct timeval. The field sec holds seconds, and usec microseconds.

Link to this type

type()

View Source (since OTP 22.0)
-type type() :: stream | dgram | raw | rdm | seqpacket.

A lowercase atom/0 representing a protocol type on the platform named SOCK_*.

Functions

Link to this function

accept(ListenSocket)

View Source (since OTP 22.0)
-spec accept(ListenSocket) -> {ok, Socket} | {error, Reason}
          when
              ListenSocket :: socket(), Socket :: socket(), Reason :: posix() | closed | invalid().

Equivalent to accept/2

Link to this function

accept/2

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec accept(ListenSocket, Timeout :: nowait) ->
          {ok, Socket} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
          when
              ListenSocket :: socket(),
              Socket :: socket(),
              SelectInfo :: select_info(),
              CompletionInfo :: completion_info(),
              Reason ::
                  posix() |
                  closed |
                  invalid() |
                  {create_accept_socket, posix()} |
                  {add_accept_socket, posix()} |
                  {update_accept_context, posix()};
      (ListenSocket, Handle :: select_handle() | completion_handle()) ->
          {ok, Socket} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
          when
              ListenSocket :: socket(),
              Socket :: socket(),
              SelectInfo :: select_info(),
              CompletionInfo :: completion_info(),
              Reason ::
                  posix() |
                  closed |
                  invalid() |
                  {create_accept_socket, posix()} |
                  {add_socket, posix()} |
                  {update_accept_context, posix()};
      (ListenSocket, Timeout :: infinity) -> {ok, Socket} | {error, Reason}
          when
              ListenSocket :: socket(),
              Socket :: socket(),
              Reason ::
                  posix() |
                  closed |
                  invalid() |
                  {create_accept_socket, posix()} |
                  {add_socket, posix()} |
                  {update_accept_context, posix()};
      (ListenSocket, Timeout :: non_neg_integer()) -> {ok, Socket} | {error, Reason}
          when
              ListenSocket :: socket(),
              Socket :: socket(),
              Reason ::
                  posix() |
                  closed |
                  invalid() |
                  timeout |
                  {create_accept_socket, posix()} |
                  {add_socket, posix()} |
                  {update_accept_context, posix()}.

Accept a connection on a socket.

This call is used with connection oriented socket types (stream or seqpacket). It returns the first pending incoming connection for a listen socket, or waits for one to arrive, and returns the (newly) connected socket.

The same as accept/1 but returns {error, timeout} if no connection has been accepted after Timeout milliseconds.

Note

On unix, note that if multiple calls are made only the last call is "valid":

      {select, {select_info, _Handle}} = socket:accept(LSock, nowait),
      {error, timeout} = socket:accept(LSock, 500),
      .
            .
      .

In the example above, Handle is not valid once the second (accept-) call has been made (the first call is automatically "cancelled" and an abort messaage sent, when the second call is made). After the (accept-) call resulting in the timeout has been made, there is no longer an active accept call!

The same as accept/1 but returns promptly.

When there is no pending connection to return, the function will return (on Unix) {select, SelectInfo} or (on Windows) {completion, CompletionInfo}, and the caller will later receive either one of these messages (depending on the platform) when the client connects:

  • select message - {'$socket', Socket, select, SelectHandle} (with the SelectHandle contained in the SelectInfo).

    A subsequent call to accept/1,2 will then return the socket.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the accept will be in the CompletionStatus.

If the time-out argument is a Handle, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding select or completion message. The Handle is presumed to be unique to this call.

If the time-out argument is nowait:

  • On Unix - And a SelectInfo is returned, it will contain a select_handle/0 generated by the call.

  • On Windows - And a CompletionInfo is returned, it will contain a completion_handle/0 generated by the call.

If the caller doesn't want to wait for a connection, it must immediately call cancel/2 to cancel the operation.

Note

On unix, note that if multiple calls are made only the last call is "valid":

      {select, {select_info, _Handle1}} = socket:accept(LSock, nowait),
      {select, {select_info, _Handle2}} = socket:accept(LSock, nowait),
      receive
          {'$socket', LSock, select, Handle2} ->
               {ok, ASock} = socket:accept(LSock, nowait),
               .
                     .
               .
      end

In the example above, only Handle2 is valid once the second (accept-) call has been made (the first call is automatically "cancelled" and an abort messaage sent, when the second call is made).

Link to this function

bind(Socket, Addr)

View Source (since OTP 22.0)
-spec bind(Socket, Addr) -> ok | {error, Reason}
        when
            Socket :: socket(),
            Addr :: sockaddr() | any | broadcast | loopback,
            Reason :: posix() | closed | invalid().

Bind a name to a socket.

When a socket is created (with open), it has no address assigned to it. bind assigns the address specified by the Addr argument.

The rules used for name binding vary between domains.

If you bind a socket to an address in for example the 'inet' or 'inet6' address families, with an ephemeral port number (0), and want to know which port that was chosen, you can find out using something like: {ok, #{port := Port}} = socket:sockname(Socket)

Link to this function

cancel/2

View Source (since OTP 22.1, OTP 26.0)
-spec cancel(Socket, SelectInfo) -> ok | {error, Reason}
          when Socket :: socket(), SelectInfo :: select_info(), Reason :: closed | invalid();
      (Socket, CompletionInfo) -> ok | {error, Reason}
          when
              Socket :: socket(),
              CompletionInfo :: completion_info(),
              Reason :: closed | invalid().

Cancel an asynchronous (select) request.

Call this function in order to cancel a previous asynchronous call to, e.g. recv/3.

An ongoing asynchronous operation blocks the socket until the operation has been finished in good order, or until it has been cancelled by this function.

Any other process that tries an operation of the same basic type (accept / send / recv) will be enqueued and notified with the regular select mechanism for asynchronous operations when the current operation and all enqueued before it has been completed.

If SelectInfo does not match an operation in progress for the calling process, this function returns {error, {invalid, SelectInfo}}.

Cancel an asynchronous (completion) request.

Call this function in order to cancel a previous asynchronous call to, e.g. recv/3.

An ongoing asynchronous operation blocks the socket until the operation has been finished in good order, or until it has been cancelled by this function.

Any other process that tries an operation of the same basic type (accept / send / recv) will be enqueued and notified with the regular select mechanism for asynchronous operations when the current operation and all enqueued before it has been completed.

If CompletionInfo does not match an operation in progress for the calling process, this function returns {error, {invalid, CompletionInfo}}.

Link to this function

cancel_monitor(MRef)

View Source (since OTP 24.0)
-spec cancel_monitor(MRef) -> boolean() when MRef :: reference().

If MRef is a reference that the calling process obtained by calling monitor/1, this monitor is turned off. If the monitoring is already turned off, nothing happens.

The returned value is one of the following:

  • true - The monitor was found and removed. In this case, no 'DOWN' message corresponding to this monitor has been delivered and will not be delivered.

  • false - The monitor was not found and could not be removed. This probably because a 'DOWN' message corresponding to this monitor has already been placed in the caller message queue.

Failure: It is an error if MRef refers to a monitor started by another process.

Link to this function

close(Socket)

View Source (since OTP 22.0)
-spec close(Socket) -> ok | {error, Reason}
         when Socket :: socket(), Reason :: posix() | closed | timeout.

Closes the socket.

Note

Note that for e.g. protocol = tcp, most implementations doing a close does not guarantee that any data sent is delivered to the recipient before the close is detected at the remote side.

One way to handle this is to use the shutdown function (socket:shutdown(Socket, write)) to signal that no more data is to be sent and then wait for the read side of the socket to be closed.

Link to this function

connect(Socket)

View Source (since OTP 24.0)
-spec connect(Socket) -> ok | {error, Reason}
           when Socket :: socket(), Reason :: posix() | closed | invalid().

This function finalizes a connection setup on a socket, after calling connect(_, _, nowait | select_handle()) that returned {select, SelectInfo}, and receiving the select message {'$socket', Socket, select, SelectHandle}, and returns whether the connection setup was successful or not.

Instead of calling this function, for backwards compatibility, it is allowed to call connect/2,3, but that incurs more overhead since the connect address and time-out are processed in vain.

Note

Not used on Windows.

Link to this function

connect(Socket, SockAddr)

View Source (since OTP 22.0)
-spec connect(Socket, SockAddr) -> ok | {error, Reason}
           when
               Socket :: socket(),
               SockAddr :: sockaddr(),
               Reason :: posix() | closed | invalid() | already.

Equivalent to connect/3

Link to this function

connect/3

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec connect(Socket, SockAddr, Timeout :: nowait) ->
           ok | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               SockAddr :: sockaddr(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason ::
                   posix() |
                   closed |
                   invalid() |
                   already | not_bound |
                   {add_socket, posix()} |
                   {update_connect_context, posix()};
       (Socket, SockAddr, Handle :: select_handle() | completion_handle()) ->
           ok | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               SockAddr :: sockaddr(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason ::
                   posix() |
                   closed |
                   invalid() |
                   already | not_bound |
                   {add_socket, posix()} |
                   {update_connect_context, posix()};
       (Socket, SockAddr, Timeout :: infinity) -> ok | {error, Reason}
           when
               Socket :: socket(),
               SockAddr :: sockaddr(),
               Reason ::
                   posix() |
                   closed |
                   invalid() |
                   already | not_bound |
                   {add_socket, posix()} |
                   {update_connect_context, posix()};
       (Socket, SockAddr, Timeout :: non_neg_integer()) -> ok | {error, Reason}
           when
               Socket :: socket(),
               SockAddr :: sockaddr(),
               Reason ::
                   posix() |
                   closed |
                   invalid() |
                   already | not_bound | timeout |
                   {add_socket, posix()} |
                   {update_connect_context, posix()}.

This function connects the socket to the address specified by the SockAddr argument, and returns when the connection has been established or failed.

If a connection attempt is already in progress (by another process), {error, already} is returned.

Note

On Windows the socket has to be bound.

The same as connect/2 but returns {error, timeout} if no connection has been established after Timeout milliseconds.

Note

On Windows the socket has to be bound.

Note that when this call has returned {error, timeout} the connection state of the socket is uncertain since the platform's network stack may complete the connection at any time, up to some platform specific time-out.

Repeating a connection attempt towards the same address would be ok, but towards a different address could end up with a connection to either address.

The safe play would be to close the socket and start over.

Also note that all this applies to cancelling a connect call with a no-wait time-out described below.

The same as connect/2 but returns promptly.

If it is not possible to immediately establish a connection, the function will return {select, SelectInfo}, and the caller will later receive a select message, {'$socket', Socket, select, SelectHandle} ( with the SelectHandle contained in the SelectInfo ) when the connection has been completed or failed. A subsequent call to connect/1 will then finalize the connection and return the result.

If the time-out argument is SelectHandle, that term will be contained in a returned SelectInfo and the corresponding select message. The SelectHandle is presumed to be unique to this call.

If the time-out argument is nowait, and a SelectInfo is returned, it will contain a select_handle() generated by the call.

If the caller doesn't want to wait for the connection to complete, it must immediately call cancel/2 to cancel the operation.

Note

On Windows the socket has to be bound.

Link to this function

getopt/2

View Source (since OTP 24.0)
-spec getopt(socket(), SocketOption :: {Level :: otp, Opt :: otp_socket_option()}) ->
          {ok, Value :: term()} | {error, invalid() | closed};
      (socket(), SocketOption :: socket_option()) ->
          {ok, Value :: term()} | {error, posix() | invalid() | closed}.

Gets a socket option from the protocol level otp, which is this implementation's level above the OS protocol layers.

See the type otp_socket_option() for a description of the options on this level.

Gets a socket option from one of the OS's protocol levels. See the type socket_option/0 for which options that this implementation knows about, how they are related to option names in the OS, and if there are known peculiarities with any of them.

What options are valid depends on what kind of socket it is (domain/0, type/0 and protocol/0).

See the socket options chapter of the users guide for more info.

Note

Not all options are valid, nor possible to get, on all platforms. That is, even if "we" support an option; it does not mean that the underlying OS does.

Link to this function

getopt/3

View Source (since OTP 22.0)
-spec getopt(socket(), otp | level(), term()) ->
          {ok, Value :: term()} | {error, posix() | invalid() | closed}.

getopt(Socket, Level, Opt) -> ok | {error, Reason}

Backwards compatibility function.

The same as getopt(Socket, {Level, Opt})

Link to this function

getopt_native/3

View Source (since OTP 24.0)
-spec getopt_native(socket(),
              SocketOption ::
                  socket_option() |
                  {Level :: level() | (NativeLevel :: integer()), NativeOpt :: integer()},
              ValueType :: integer) ->
                 {ok, Value :: integer()} | {error, posix() | invalid() | closed};
             (socket(),
              SocketOption ::
                  socket_option() |
                  {Level :: level() | (NativeLevel :: integer()), NativeOpt :: integer()},
              ValueType :: boolean) ->
                 {ok, Value :: boolean()} | {error, posix() | invalid() | closed};
             (socket(),
              SocketOption ::
                  socket_option() |
                  {Level :: level() | (NativeLevel :: integer()), NativeOpt :: integer()},
              ValueSize :: non_neg_integer()) ->
                 {ok, Value :: binary()} | {error, posix() | invalid() | closed};
             (socket(),
              SocketOption ::
                  socket_option() |
                  {Level :: level() | (NativeLevel :: integer()), NativeOpt :: integer()},
              ValueSpec :: binary()) ->
                 {ok, Value :: binary()} | {error, posix() | invalid() | closed}.

Gets a socket option that may be unknown to our implementation, or that has a type not compatible with our implementation, that is; in "native mode".

The socket option may be specified with an ordinary socket_option() tuple, with a known Level = level() and an integer NativeOpt, or with both an integer NativeLevel and NativeOpt.

How to decode the option value has to be specified either with ValueType, by specifying the ValueSize for a binary/0 that will contain the fetched option value, or by specifying a binary/0 ValueSpec that will be copied to a buffer for the getsockopt() call to write the value in which will be returned as a new binary/0.

If ValueType is integer a C type (int) will be fetched, if it is boolean a C type (int) will be fetched and converted into a boolean/0 according to the C implementation.

What options are valid depends on what kind of socket it is (domain/0, type/0 and protocol/0).

The integer values for NativeLevel and NativeOpt as well as the Value encoding has to be deduced from the header files for the running system.

-spec i() -> ok.

Print all sockets in table format in the erlang shell.

-spec i(InfoKeys) -> ok when InfoKeys :: info_keys();
 (Domain) -> ok when Domain :: inet | inet6 | local;
 (Proto) -> ok when Proto :: sctp | tcp | udp;
 (Type) -> ok when Type :: dgram | seqpacket | stream.

Print all sockets in table format in the erlang shell. What information is included is defined by InfoKeys.

Print a selection, based on domain, of the sockets in table format in the erlang shell.

Print a selection, based on protocol, of the sockets in table format in the erlang shell.

Print a selection, based on type, of the sockets in table format in the erlang shell.

-spec i(Domain, InfoKeys) -> ok when Domain :: inet | inet6 | local, InfoKeys :: info_keys();
 (Proto, InfoKeys) -> ok when Proto :: sctp | tcp | udp, InfoKeys :: info_keys();
 (Type, InfoKeys) -> ok when Type :: dgram | seqpacket | stream, InfoKeys :: info_keys().

Print a selection, based on domain, of the sockets in table format in the erlang shell. What information is included is defined by InfoKeys.

Print a selection, based on domain, of the sockets in table format in the erlang shell. What information is included is defined by InfoKeys.

Print a selection, based on type, of the sockets in table format in the erlang shell. What information is included is defined by InfoKeys.

-spec info() -> info().

Get miscellaneous info about the socket library.

The function returns a map with each info item as a key-value binding.

Note

In order to ensure data integrity, mutex'es are taken when needed. So, do not call this function often.

Link to this function

info(Socket)

View Source (since OTP 22.1)
-spec info(Socket) -> socket_info() when Socket :: socket().

Get miscellaneous info about the socket.

The function returns a map with each info item as a key-value binding. It reflects the "current" state of the socket.

Note

In order to ensure data integrity, mutex'es are taken when needed. So, do not call this function often.

Link to this function

ioctl/2

View Source (since OTP 24.2,OTP 26.1)
-spec ioctl(Socket, GetRequest :: gifconf) ->
         {ok, IFConf :: [#{name := string, addr := sockaddr()}]} | {error, Reason}
         when Socket :: socket(), Reason :: posix() | closed;
     (Socket, GetRequest :: nread | nwrite | nspace) ->
         {ok, NumBytes :: non_neg_integer()} | {error, Reason}
         when Socket :: socket(), Reason :: posix() | closed;
     (Socket, GetRequest :: atmark) -> {ok, Available :: boolean()} | {error, Reason}
         when Socket :: socket(), Reason :: posix() | closed;
     (Socket, GetRequest :: tcp_info) -> {ok, Info :: map()} | {error, Reason}
         when Socket :: socket(), Reason :: posix() | closed.

Retrieve socket (device) parameters.

This function retrieves a specific parameter, according to GetRequest argument.

  • gifconf - Return a list of interface (transport layer) addresses.

    Result, a list of interfaces, map with name and address.

  • nread - Get the number of bytes that are immediately available for reading.

    Result, number of bytes, is a integer/0.

  • nwrite - The number of bytes in the send queue.

    Result, number of bytes, is a integer/0.

  • nspace - Get the free space in the send queue.

    Result, number of bytes, is a integer/0.

  • atmark - Test if there is oob (out-of-bound) data waiting to be read.

    Result is a boolean/0.

  • tcp_info - Return miscellaneous TCP related information for a connected socket.

    Result is a map/0.

Note

To see if a ioctl request is supported on the current platform:

      Request = nread,
      {ok, true} = socket:is_supported(ioctl_requests, Request),
      .
      .
      .
Link to this function

ioctl/3

View Source (since OTP 24.2, OTP 26.1)
-spec ioctl(Socket, GetRequest, NameOrIndex) -> {ok, Result} | {error, Reason}
         when
             Socket :: socket(),
             GetRequest ::
                 gifname | gifindex | gifaddr | gifdstaddr | gifbrdaddr | gifnetmask | gifhwaddr |
                 gifmtu | giftxqlen | gifflags | tcp_info,
             NameOrIndex :: string() | integer(),
             Result :: term(),
             Reason :: posix() | closed;
     (Socket, SetRequest, Value) -> ok | {error, Reason}
         when
             Socket :: socket(),
             SetRequest :: rcvall,
             Value :: off | on | iplevel,
             Reason :: posix() | closed;
     (Socket, SetRequest, Value) -> ok | {error, Reason}
         when
             Socket :: socket(),
             SetRequest :: rcvall_igmpmcast | rcvall_mcast,
             Value :: off | on,
             Reason :: posix() | closed.

Retrieve socket (device) parameters.

This function retrieves a specific parameter, according to GetRequest argument. The third argument is a the (lookup) "key", identifying the interface (usually the name of the interface) or a command to set.

  • gifname - Get the name of the interface with the specified index (integer()).

    Result, name of the interface, is a string/0.

  • gifindex - Get the index of the interface with the specified name.

    Result, interface index, is a integer/0.

  • gifaddr - Get the address of the interface with the specified name. Result, address of the interface, is a socket:sockaddr().

  • gifdstaddr - Get the destination address of the point-to-point interface with the specified name.

    Result, destination address of the interface, is a socket:sockaddr().

  • gifbrdaddr - Get the droadcast address for the interface with the specified name.

    Result, broadcast address of the interface, is a socket:sockaddr().

  • gifnetmask - Get the network mask for the interface with the specified name.

    Result, network mask of the interface, is a socket:sockaddr().

  • gifhwaddr - Get the hardware address for the interface with the specified name.

    Result, hardware address of the interface, is a socket:sockaddr(). The family field contains the 'ARPHRD' device type (or an integer).

  • gifmtu - Get the MTU (Maximum Transfer Unit) for the interface with the specified name.

    Result, MTU of the interface, is an integer/0.

  • giftxqlen - Get the transmit queue length of the interface with the specified name.

    Result, transmit queue length of the interface, is an integer/0.

  • gifflags - Get the active flag word of the interface with the specified name.

    Result, the active flag word of the interface, is an list of socket:ioctl_device_flag() | integer().

Set socket (device) parameters.

This function sets a specific parameter, according to SetRequest argument. The third argument is the value to set.

  • rcvall - Enables (or disables) a socket to receive all IPv4 or IPv6 packages passing through a network interface.

    The socket has to be either one of:

    • An IPv4 socket - Created with the address family of inet, socket type of raw and protocol set to ip.

    • An IPv6 socket - Created with the address family of inet6, socket type of raw and protocol set to ipv6.

    The socket must also be bound to an (explicit) local IPv4 or IPv6 interface (any not allowed).

    Setting this IOCTL requires admin privileges.

Set socket (device) parameters.

This function sets a specific parameter, according to SetRequest argument. The third argument is the value to set.

  • rcvall_igmpmcall - Enables (or disables) a socket to receive IGMP multicast IP traffic, without receiving any other IP traffic.

    The socket has to be created with the address family of inet, socket type of raw and protocol set to igmp.

    The socket must also be bound to an (explicit) local interface (any not allowed).

    Must have a sufficiently large buffer.

    Setting this IOCTL requires admin privileges.

  • rcvall_mcall - Enables (or disables) a socket to receive all multicast IP traffic (as in; all IP packets destined for IP addresses in the range of 224.0.0.0 to 239.255.255.255).

    The socket has to be created with the address family of inet, socket type of raw and protocol set to udp.

    The socket must also be bound to an (explicit) local interface (any not allowed). And bind to port zero

    Must have a sufficiently large buffer.

    Setting this IOCTL requires admin privileges.

Link to this function

ioctl(Socket, SetRequest, Name, Value)

View Source (since OTP 24.2)
-spec ioctl(Socket, SetRequest, Name, Value) -> ok | {error, Reason}
         when
             Socket :: socket(),
             SetRequest ::
                 sifflags | sifaddr | sifdstaddr | sifbrdaddr | sifnetmask | sifhwaddr | gifmtu |
                 siftxqlen,
             Name :: string(),
             Value :: term(),
             Reason :: posix() | closed.

Set socket (device) parameters. This function sets a specific parameter, according to SetRequest argument. The third argument is the "key", identifying the interface (usually the name of the interface), and the fourth is the "new" value.

These are privileged operation's.

  • sifflags - Set the the active flag word, #{Flag => boolean()}, of the interface with the specified name.

    Each flag to be changed, should be added to the value map, with the value 'true' if the flag (Flag) should be set and 'false' if the flag should be reset.

  • sifaddr - Set the address, sockaddr/0, of the interface with the specified name.

  • sifdstaddr - Set the destination address, sockaddr/0, of a point-to-point interface with the specified name.

  • sifbrdaddr - Set the broadcast address, sockaddr/0, of the interface with the specified name.

  • sifnetmask - Set the network mask, sockaddr/0, of the interface with the specified name.

  • sifmtu - Set the MTU (Maximum Transfer Unit), integer/0, for the interface with the specified name.

  • siftxqlen - Set the transmit queue length, integer/0, of the interface with the specified name.

Link to this function

is_supported(Key1)

View Source (since OTP 23.0)
-spec is_supported(Key1 :: term()) -> boolean().

Equivalent to is_supported/2

Link to this function

is_supported(Key1, Key2)

View Source (since OTP 23.0)
-spec is_supported(Key1 :: term(), Key2 :: term()) -> boolean().

This function retrieves information about what the platform supports, such as if SCTP is supported, or if a socket options are supported.

For keys other than the known false is returned. Note that in a future version or on a different platform there might be more supported items.

This functions returns a boolean corresponding to what supports/0-2 reports for the same Key1 (and Key2).

Link to this function

listen(Socket)

View Source (since OTP 22.0)
-spec listen(Socket) -> ok | {error, Reason}
          when Socket :: socket(), Reason :: posix() | closed | not_bound.

Equivalent to listen/2

Link to this function

listen(Socket, Backlog)

View Source (since OTP 22.0)
-spec listen(Socket, Backlog) -> ok | {error, Reason}
          when Socket :: socket(), Backlog :: integer(), Reason :: posix() | closed.

Listen for connections on a socket.

Note

On Windows the socket has to be bound.

Link to this function

monitor(Socket)

View Source (since OTP 24.0)
-spec monitor(Socket) -> reference() when Socket :: socket().

Start monitor the socket Socket.

If the monitored socket does not exist or when the monitor is triggered, a 'DOWN' message is sent that has the following pattern:

	    {'DOWN', MonitorRef, socket, Object, Info}

In the monitor message MonitorRef and Type are the same as described earlier, and:

  • Object - The monitored entity, socket, which triggered the event.

  • Info - Either the termination reason of the socket or nosock (socket Socket did not exist at the time of monitor creation).

Making several calls to socket:monitor/1 for the same Socket is not an error; it results in as many independent monitoring instances.

Link to this function

number_of()

View Source (since OTP 22.3)
-spec number_of() -> non_neg_integer().

Returns the number of active sockets.

Link to this function

open(FD)

View Source (since OTP 23.0)
-spec open(FD) -> {ok, Socket} | {error, Reason}
        when FD :: integer(), Socket :: socket(), Reason :: posix() | domain | type | protocol.

Equivalent to open/2

Link to this function

open/2

View Source (since OTP 22.0,OTP 24.0)
-spec open(FD, Opts) -> {ok, Socket} | {error, Reason}
        when
            FD :: integer(),
            Opts ::
                #{domain => domain() | integer(),
                  type => type() | integer(),
                  protocol => default | protocol() | integer(),
                  dup => boolean(),
                  debug => boolean(),
                  use_registry => boolean()},
            Socket :: socket(),
            Reason :: posix() | domain | type | protocol;
    (Domain, Type) -> {ok, Socket} | {error, Reason}
        when
            Domain :: domain() | integer(),
            Type :: type() | integer(),
            Socket :: socket(),
            Reason :: posix() | protocol.

Creates an endpoint (socket) for communication based on an already existing file descriptor. The function attempts to retrieve domain, type and protocol from the system. This is however not possible on all platforms, and they should then be specified in Opts.

The Opts argument is intended for providing extra information for the open call:

  • domain - Which protocol domain is the descriptor of. See also open/2,3,4.

  • type - Which protocol type type is the descriptor of.

    See also open/2,3,4.

  • protocol - Which protocol is the descriptor of. The atom default is equivalent to the integer protocol number 0 which means the default protocol for a given domain and type.

    If the protocol can not be retrieved from the platform for the socket, and protocol is not specified, the default protocol is used, which may or may not be correct.

    See also open/2,3,4.

  • dup - Shall the provided descriptor be duplicated (dup) or not.
    Defaults to true.

  • debug - Enable or disable debug during the open call.
    Defaults to false.

  • use_registry - Enable or disable use of the socket registry for this socket. This overrides the global value.
    Defaults to the global value, see use_registry/1.

Note

This function should be used with care!

On some platforms it is necessary to provide domain, type and protocol since they cannot be retrieved from the platform.

-spec open(Domain, Type, Opts) -> {ok, Socket} | {error, Reason}
        when
            Domain :: domain() | integer(),
            Type :: type() | integer(),
            Opts :: map(),
            Socket :: socket(),
            Reason :: posix() | protocol;
    (Domain, Type, Protocol) -> {ok, Socket} | {error, Reason}
        when
            Domain :: domain() | integer(),
            Type :: type() | integer(),
            Protocol :: default | protocol() | integer(),
            Socket :: socket(),
            Reason :: posix() | protocol.

Creates an endpoint (socket) for communication.

The same as open(Domain, Type, default) and open(Domain, Type, default, Opts) respectively.

Link to this function

open(Domain, Type, Protocol, Opts)

View Source (since OTP 22.0)
-spec open(Domain, Type, Protocol, Opts) -> {ok, Socket} | {error, Reason}
        when
            Domain :: domain() | integer(),
            Type :: type() | integer(),
            Protocol :: default | protocol() | integer(),
            Opts :: #{netns => string(), debug => boolean(), use_registry => boolean()},
            Socket :: socket(),
            Reason :: posix() | protocol.

Creates an endpoint (socket) for communication.

Domain and Type may be integer/0s, as defined in the platform's header files. The same goes for Protocol as defined in the platform's services(5) database. See also the OS man page for the library call socket(2).

Note

For some combinations of Domain and Type the platform has got a default protocol that can be selected with Protocol = default, and the platform may allow or require selecting the default protocol, a specific protocol, or either.

Examples:

  • socket:open(inet, stream, tcp) - It is common that for protocol domain and type inet,stream it is allowed to select the tcp protocol although that mostly is the default.
  • socket:open(local, dgram) - It is common that for the protocol domain local it is mandatory to not select a protocol, that is; to select the default protocol.

The Opts argument is intended for "other" options. The supported option(s) are described below:

  • netns: string() - Used to set the network namespace during the open call. Only supported on the Linux platform.

  • debug: boolean() - Enable or disable debug during the open call.
    Defaults to false.

  • use_registry: boolean() - Enable or disable use of the socket registry for this socket. This overrides the global value.
    Defaults to the global value, see use_registry/1.

Link to this function

peername(Socket)

View Source (since OTP 22.0)
-spec peername(Socket) -> {ok, SockAddr} | {error, Reason}
            when Socket :: socket(), SockAddr :: sockaddr_recv(), Reason :: posix() | closed.

Returns the address of the peer connected to the socket.

Link to this function

recv(Socket)

View Source (since OTP 22.0,OTP 24.0)
-spec recv(Socket) -> {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when Socket :: socket(), Data :: binary(), Reason :: posix() | closed | invalid().

Equivalent to recv/4

Link to this function

recv/2

View Source (since OTP 22.0,OTP 24.0)
-spec recv(Socket, Flags) -> {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Length) -> {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Data :: binary(),
            Reason :: posix() | closed | invalid().

Equivalent to recv/4

Link to this function

recv/3

View Source (since OTP 22.1,OTP 24.0)
-spec recv(Socket, Flags, Handle :: nowait) ->
        {ok, Data} |
        {select, SelectInfo} |
        {select, {SelectInfo, Data}} |
        {completion, CompletionInfo} |
        {error, Reason} |
        {error, {Reason, Data}}
        when
            Socket :: socket(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Flags, Handle :: select_handle() | completion_handle()) ->
        {ok, Data} |
        {select, SelectInfo} |
        {select, {SelectInfo, Data}} |
        {completion, CompletionInfo} |
        {error, Reason} |
        {error, {Reason, Data}}
        when
            Socket :: socket(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Flags, Timeout :: infinity) -> {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Flags, Timeout :: non_neg_integer()) ->
        {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            Reason :: posix() | closed | invalid() | timeout;
    (Socket, Length, Flags) -> {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Handle :: nowait) ->
        {ok, Data} |
        {select, SelectInfo} |
        {select, {SelectInfo, Data}} |
        {completion, CompletionInfo} |
        {error, Reason} |
        {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Data :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Handle :: select_handle() | completion_handle()) ->
        {ok, Data} |
        {select, SelectInfo} |
        {select, {SelectInfo, Data}} |
        {completion, CompletionInfo} |
        {error, Reason} |
        {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Data :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Timeout :: infinity) ->
        {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Data :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Timeout :: non_neg_integer()) ->
        {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Data :: binary(),
            Reason :: posix() | closed | invalid() | timeout.

Equivalent to recv/4

Link to this function

recv/4

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec recv(Socket, Length, Flags, Handle :: nowait) ->
        {ok, Data} |
        {select, SelectInfo} |
        {select, {SelectInfo, Data}} |
        {completion, CompletionInfo} |
        {error, Reason} |
        {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Flags, Handle :: select_handle() | completion_handle()) ->
        {ok, Data} |
        {select, SelectInfo} |
        {select, {SelectInfo, Data}} |
        {completion, CompletionInfo} |
        {error, Reason} |
        {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Flags, Timeout :: infinity) ->
        {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Length, Flags, Timeout :: non_neg_integer()) ->
        {ok, Data} | {error, Reason} | {error, {Reason, Data}}
        when
            Socket :: socket(),
            Length :: non_neg_integer(),
            Flags :: [msg_flag() | integer()],
            Data :: binary(),
            Reason :: posix() | closed | invalid() | timeout.

Receives data from a socket, waiting for it to arrive.

The argument Length specifies how many bytes to receive, with the special case 0 meaning "all available".

For a socket of type stream this call will not return until all requested data can be delivered, or if "all available" data was requested when the first data chunk arrives.

The message Flags may be symbolic msg_flag/0s and/or integer/0s, as in the platform's appropriate header files. The values of all symbolic flags and integers are or:ed together.

When there is a socket error this function returns {error, Reason}, or if some data arrived before the error; {error, {Reason, Data}}.

Receives data from a socket, waiting at most Timeout milliseconds for it to arrive.

The same as infinite time-out recv/1,2,3,4 but returns {error, timeout} or {error, {timeout, Data}} after Timeout milliseconds, if the requested data has not been delivered.

Receives data from a socket, but returns a select or completion continuation if the data could not be returned immediately.

The same as infinite time-out recv/1,2,3,4 but if the data can be delivered immediately, the function returns (on Unix) {select,  SelectInfo} or (on Windows) {completion,  CompletionInfo}, and the caller will then receive one of these messages:

  • select message - {'$socket', Socket, select, SelectHandle} (with the SelectHandle that was contained in the SelectInfo) when data has arrived.

    A subsequent call to recv/1,2,3,4 will then return the data.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the receive will be in the CompletionStatus.

If Handle is a select_handle/0 or completion_handle/0, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding (select or completion) message. The Handle is presumed to be unique to this call.

If the time-out argument is nowait, and a SelectInfo or CompletionInfo is returned, it will contain a select_handle/0 or completion_handle/0 generated by the call.

Note that for a socket of type stream (on Unix), if Length > 0 and only part of that amount of data is available, the function will return {ok, {Data, SelectInfo}} with partial data. If the caller doesn't want to wait for more data, it must immediately call cancel/2 to cancel the operation.

Link to this function

recvfrom(Socket)

View Source (since OTP 22.0,OTP 24.0)
-spec recvfrom(Socket) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid().

Equivalent to recvfrom/4

Link to this function

recvfrom/2

View Source (since OTP 22.0,OTP 24.0)
-spec recvfrom(Socket, Flags) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid().

Equivalent to recvfrom/4

Link to this function

recvfrom/3

View Source (since OTP 22.1,OTP 24.0)
-spec recvfrom(Socket, Flags, Handle :: nowait) ->
            {ok, {Source, Data}} |
            {select, SelectInfo} |
            {completion, CompletionInfo} |
            {error, Reason}
            when
                Socket :: socket(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                SelectInfo :: select_info(),
                CompletionInfo :: completion_info(),
                Reason :: posix() | closed | invalid();
        (Socket, Flags, Handle :: select_handle() | completion_handle()) ->
            {ok, {Source, Data}} |
            {select, SelectInfo} |
            {completion, CompletionInfo} |
            {error, Reason}
            when
                Socket :: socket(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                SelectInfo :: select_info(),
                CompletionInfo :: completion_info(),
                Reason :: posix() | closed | invalid();
        (Socket, Flags, Timeout :: infinity) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid();
        (Socket, Flags, Timeout :: non_neg_integer()) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid() | timeout;
        (Socket, BufSz, Flags) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Handle :: nowait) ->
            {ok, {Source, Data}} |
            {select, SelectInfo} |
            {completion, CompletionInfo} |
            {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Source :: sockaddr_recv(),
                Data :: binary(),
                SelectInfo :: select_info(),
                CompletionInfo :: completion_info(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Handle :: select_handle() | completion_handle()) ->
            {ok, {Source, Data}} |
            {select, SelectInfo} |
            {completion, CompletionInfo} |
            {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Source :: sockaddr_recv(),
                Data :: binary(),
                SelectInfo :: select_info(),
                CompletionInfo :: completion_info(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Timeout :: infinity) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Timeout :: non_neg_integer()) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid() | timeout.

Equivalent to recvfrom/4

Link to this function

recvfrom/4

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec recvfrom(Socket, BufSz, Flags, Handle :: nowait) ->
            {ok, {Source, Data}} |
            {select, SelectInfo} |
            {completion, CompletionInfo} |
            {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                SelectInfo :: select_info(),
                CompletionInfo :: completion_info(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Flags, Handle :: select_handle() | completion_handle()) ->
            {ok, {Source, Data}} |
            {select, SelectInfo} |
            {completion, CompletionInfo} |
            {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                SelectInfo :: select_info(),
                CompletionInfo :: completion_info(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Flags, Timeout :: infinity) -> {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid();
        (Socket, BufSz, Flags, Timeout :: non_neg_integer()) ->
            {ok, {Source, Data}} | {error, Reason}
            when
                Socket :: socket(),
                BufSz :: non_neg_integer(),
                Flags :: [msg_flag() | integer()],
                Source :: sockaddr_recv(),
                Data :: binary(),
                Reason :: posix() | closed | invalid() | timeout.

Receive a message from a socket, waiting for it to arrive.

The function returns when a message is received, or when there is a socket error. Argument BufSz specifies the number of bytes for the receive buffer. If the buffer size is too small, the message will be truncated.

If BufSz is not specified or 0, a default buffer size is used, which can be set by socket:setopt(Socket, {otp,recvbuf}, BufSz).

If it is impossible to know the appropriate buffer size, it may be possible to use the receive message flag peek. When this flag is used, the message is not "consumed" from the underlying buffers, so another recvfrom/1,2,3,4 call is needed, possibly with an adjusted buffer size.

The message Flags may be symbolic msg_flag/0s and/or integer/0s, as in the platform's appropriate header files. The values of all symbolic flags and integers are or:ed together.

Receives a message from a socket, waiting at most Timeout milliseconds for it to arrive.

The same as infinite time-out recvfrom/1,2,3,4 but returns {error, timeout} after Timeout milliseconds, if no message has been delivered.

Receives a message from a socket, but returns a select continuation or a completion term if no message could be returned immediately.

The same as infinite time-out recvfrom/1,2,3,4 but if no message can be delivered immediately, the function returns (on /Unix) {select, SelectInfo} or (on Windows) {completion,  CompletionInfo}, and the caller will then receive one of these messages:

  • select message - {'$socket', Socket, select, SelectHandle} (with the SelectHandle that was contained in the SelectInfo) when data has arrived.

    A subsequent call to recvfrom/1,2,3,4 will then return the message.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the receive will be in the CompletionStatus.

If the Handle is a select_handle/0 or completion_handle/0, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding (select or completion) message. The Handle is presumed to be unique to this call.

If the time-out argument is nowait, and a SelectInfo or CompletionInfo is returned, it will contain a select_handle/0 or completion_handle/0 generated by the call.

If the caller doesn't want to wait for the data, it must immediately call cancel/2 to cancel the operation.

Link to this function

recvmsg(Socket)

View Source (since OTP 22.0,OTP 24.0)
-spec recvmsg(Socket) -> {ok, Msg} | {error, Reason}
           when Socket :: socket(), Msg :: msg_recv(), Reason :: posix() | closed | invalid().

Equivalent to recvmsg/5

Link to this function

recvmsg/2

View Source (since OTP 22.1,OTP 24.0)
-spec recvmsg(Socket, Flags) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid();
       (Socket, Timeout :: nowait) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Handle :: select_handle() | completion_handle()) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Timeout :: infinity) -> {ok, Msg} | {error, Reason}
           when Socket :: socket(), Msg :: msg_recv(), Reason :: posix() | closed | invalid();
       (Socket, Timeout :: non_neg_integer()) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid() | timeout.

Equivalent to recvmsg/5

Link to this function

recvmsg/3

View Source (since OTP 22.1,OTP 24.0)
-spec recvmsg(Socket, Flags, Timeout :: nowait) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Flags, Handle :: select_handle() | completion_handle()) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Flags, Timeout :: infinity) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid();
       (Socket, Flags, Timeout :: non_neg_integer()) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid() | timeout;
       (Socket, BufSz, CtrlSz) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid().

Equivalent to recvmsg/5

Link to this function

recvmsg(Socket, BufSz, CtrlSz, Timeout)

View Source (since OTP 22.1,OTP 24.0)
-spec recvmsg(Socket, BufSz, CtrlSz, Timeout :: nowait) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, BufSz, CtrlSz, Handle :: select_handle() | completion_handle()) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, BufSz, CtrlSz, Timeout :: infinity) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid();
       (Socket, BufSz, CtrlSz, Timeout :: non_neg_integer()) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid() | timeout.

Equivalent to recvmsg/5

Link to this function

recvmsg/5

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec recvmsg(Socket, BufSz, CtrlSz, Flags, Timeout :: nowait) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, BufSz, CtrlSz, Flags, Handle :: select_handle() | completion_handle()) ->
           {ok, Msg} | {select, SelectInfo} | {completion, CompletionInfo} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, BufSz, CtrlSz, Flags, Timeout :: infinity) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid();
       (Socket, BufSz, CtrlSz, Flags, Timeout :: non_neg_integer()) -> {ok, Msg} | {error, Reason}
           when
               Socket :: socket(),
               BufSz :: non_neg_integer(),
               CtrlSz :: non_neg_integer(),
               Flags :: [msg_flag() | integer()],
               Msg :: msg_recv(),
               Reason :: posix() | closed | invalid() | timeout.

Receive a message from a socket, waiting for it to arrive.

The function returns when a message is received, or when there is a socket error. Arguments BufSz and CtrlSz specifies the number of bytes for the receive buffer and the control message buffer. If the buffer size(s) is(are) too small, the message and/or control message list will be truncated.

If BufSz is not specified or 0, a default buffer size is used, which can be set by socket:setopt(Socket, {otp,recvbuf}, BufSz). The same applies to CtrlSz and socket:setopt(Socket, {otp,recvctrlbuf}, CtrlSz).

If it is impossible to know the appropriate buffer size, it may be possible to use the receive message flag peek. When this flag is used, the message is not "consumed" from the underlying buffers, so another recvfrom/1,2,3,4,5 call is needed, possibly with an adjusted buffer size.

The message Flags may be symbolic msg_flag/0s and/or integer/0s, as in the platform's appropriate header files. The values of all symbolic flags and integers are or:ed together.

Receives a message from a socket, waiting at most Timeout milliseconds for it to arrive.

The same as recvmsg/1,2,3,4,5 but returns {error, timeout} after Timeout milliseconds, if no message has been delivered.

Receives a message from a socket, but returns a select continuation or a completion term if no message could be returned immediately.

The same as infinite time-out recvmsg/1,2,3,4 but if no message can delivered immediately, the function returns (on Unix) {select, SelectInfo} or (on Windows) {completion,  CompletionInfo}, and the caller will then receive one of these messages:

  • select message - {'$socket', Socket, select, SelectHandle} (with the SelectHandle that was contained in the SelectInfo) when data has arrived.

    A subsequent call to recvmsg/1,2,3,4,5 will then return the data.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the receive will be in the CompletionStatus.

If the Handle is a select_handle/0 or completion_handle/0, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding (select or completion) message. The Handle is presumed to be unique to this call.

If the time-out argument is nowait, and a SelectInfo or CompletionInfo is returned, it will contain a select_handle/0 or completion_handle/0 generated by the call.

If the caller doesn't want to wait for the data, it must immediately call cancel/2 to cancel the operation.

Link to this function

send(Socket, Data)

View Source (since OTP 22.0)
-spec send(Socket, Data) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            RestData :: binary(),
            Reason :: posix() | closed | invalid().

Equivalent to send/4

-spec send(Socket, Data, Flags) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            Flags :: [msg_flag() | integer()],
            RestData :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Data, Cont) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            Cont :: select_info(),
            RestData :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Data, Handle :: nowait) ->
        ok |
        {ok, RestData} |
        {select, SelectInfo} |
        {select, {SelectInfo, RestData}} |
        {completion, CompletionInfo} |
        {error, Reason}
        when
            Socket :: socket(),
            Data :: iodata(),
            RestData :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Handle :: select_handle() | completion_handle()) ->
        ok |
        {ok, RestData} |
        {select, SelectInfo} |
        {select, {SelectInfo, RestData}} |
        {completion, CompletionInfo} |
        {error, Reason}
        when
            Socket :: socket(),
            Data :: iodata(),
            RestData :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Timeout :: infinity) ->
        ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            RestData :: binary(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Timeout :: non_neg_integer()) ->
        ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            RestData :: binary(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei().

Equivalent to send/4

Link to this function

send/4

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec send(Socket, Data, Flags, Handle :: nowait) ->
        ok |
        {ok, RestData} |
        {select, SelectInfo} |
        {select, {SelectInfo, RestData}} |
        {completion, CompletionInfo} |
        {error, Reason}
        when
            Socket :: socket(),
            Data :: iodata(),
            Flags :: [msg_flag() | integer()],
            RestData :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Flags, Handle :: select_handle() | completion_handle()) ->
        ok |
        {ok, RestData} |
        {select, SelectInfo} |
        {select, {SelectInfo, RestData}} |
        {completion, CompletionInfo} |
        {error, Reason}
        when
            Socket :: socket(),
            Data :: iodata(),
            Flags :: [msg_flag() | integer()],
            RestData :: binary(),
            SelectInfo :: select_info(),
            CompletionInfo :: completion_info(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Flags, Timeout :: infinity) ->
        ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            Flags :: [msg_flag() | integer()],
            RestData :: binary(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Flags, Timeout :: non_neg_integer()) ->
        ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            Flags :: [msg_flag() | integer()],
            RestData :: binary(),
            Reason :: posix() | closed | invalid() | netname_deleted | too_many_cmds | eei();
    (Socket, Data, Cont, SelectHandle :: nowait) ->
        ok |
        {ok, RestData} |
        {select, SelectInfo} |
        {select, {SelectInfo, RestData}} |
        {error, Reason}
        when
            Socket :: socket(),
            Data :: iodata(),
            Cont :: select_info(),
            RestData :: binary(),
            SelectInfo :: select_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Data, Cont, SelectHandle :: select_handle()) ->
        ok |
        {ok, RestData} |
        {select, SelectInfo} |
        {select, {SelectInfo, RestData}} |
        {error, Reason}
        when
            Socket :: socket(),
            Data :: iodata(),
            Cont :: select_info(),
            RestData :: binary(),
            SelectInfo :: select_info(),
            Reason :: posix() | closed | invalid();
    (Socket, Data, Cont, Timeout :: infinity) ->
        ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            Cont :: select_info(),
            RestData :: binary(),
            Reason :: posix() | closed | invalid();
    (Socket, Data, Cont, Timeout :: non_neg_integer()) ->
        ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
        when
            Socket :: socket(),
            Data :: iodata(),
            Cont :: select_info(),
            RestData :: binary(),
            Reason :: posix() | closed | invalid().

Sends data on a connected socket, waiting for it to be sent.

This call will not return until the Data has been accepted by the platform's network layer, or it reports an error.

The message Flags may be symbolic msg_flag/0s and/or integer/0s, matching the platform's appropriate header files. The values of all symbolic flags and integers are or:ed together.

The Data, if it is not a binary/0, is copied into one before calling the platform network API, because a single buffer is required. A returned RestData is a sub binary of this data binary.

The return value indicates the result from the platform's network layer:

  • ok - All data has been accepted.

  • {ok, RestData} - Not all data has been accepted, but no error has been reported. RestData is the tail of Data that has not been accepted.

    This cannot happen for a socket of type stream where a partially successful send is retried until the data is either accepted or there is an error.

    For a socket of type dgram this should probably also not happen since a message that cannot be passed atomically should render an error.

    It is nevertheless possible for the platform's network layer to return this.

  • {error, Reason} - An error has been reported and no data has been accepted. The posix/0 Reasons are from the platform's network layer. closed means that this socket library knows that the socket is closed, and invalid/0 means that something about an argument is invalid.

  • {error, {Reason, RestData}} - An error has been reported but before that some data was accepted. RestData is the tail of Data that has not been accepted. See {error, Reason} above.

    This can only happen for a socket of type stream when a partially successful send is retried until there is an error.

Sends data on a connected socket, waiting at most Timeout milliseconds for it to be sent.

The same as infinite time-out send/2,3,4 but returns {error, timeout} or {error, {timeout, RestData}} after Timeout milliseconds, if no Data or only some of it was accepted by the platform's network layer.

Sends data on a connected socket, but returns completion or a select continuation if the data could not be sent immediately.

The same as infinite time-out send/2,3 but if the data is not immediately accepted by the platform network layer, the function returns (on Unix) {select, SelectInfo} or (on Windows) {completion, CompletionInfo}, and the caller will then receive one of these messages:

  • select message - {'$socket', Socket, select, SelectHandle} ( with the SelectHandle that was contained in the SelectInfo ) when there is room for more data.

    A subsequent call to send/2-4 will then send the data.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the send will be in the CompletionStatus.

If Handle is a select_handle/0 or completion_handle/0, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding select or completion message. The Handle is presumed to be unique to this call.

If Handle is nowait, and a SelectInfo or CompletionInfo is returned, it will contain a select_handle/0 or completion_handle/0 generated by the call.

If some of the data was sent, the function will return {select, {RestData, SelectInfo},which can only happen (on Unix) for a socket of type stream. If the caller does not want to wait to send the rest of the data, it should immediately cancel the operation with cancel/2.

Continues sending data on a connected socket, where the send operation was initiated by send/3,4 that returned a SelectInfo continuation. Otherwise like infinite time-out send/2,3,4 , limited time-out send/3,4 or nowait send/3,4 respectively.

Cont is the SelectInfo that was returned from the previous send() call.

If Data is not a binary/0, it will be copied into one, again.

The return value indicates the result from the platform's network layer. See send/2,3,4 and nowait send/3,4.

Link to this function

sendfile(Socket, FileHandle)

View Source (since OTP 24.0)
-spec sendfile(socket(), file:fd()) -> {ok, BytesSent} | {error, Reason} | {error, {Reason, BytesSent}}
            when Reason :: posix() | closed | invalid(), BytesSent :: non_neg_integer().

sendfile(Socket, FileHandle) -> Result

The same as sendfile(Socket, FileHandle, 0, 0, infinity), that is: send all data in the file to the socket, without time-out other than from the platform's network stack.

Link to this function

sendfile(Socket, FileHandle, Timeout)

View Source (since OTP 24.0)
-spec sendfile(socket(), file:fd(), Timeout) ->
            {ok, BytesSent} |
            {select, SelectInfo} |
            {select, {SelectInfo, BytesSent}} |
            {error, Reason} |
            {error, {Reason, BytesSent}}
            when
                SelectInfo :: select_info(),
                Timeout :: timeout() | nowait | select_handle(),
                Reason :: posix() | closed | invalid() | timeout,
                BytesSent :: non_neg_integer().

Depending on the Timeout argument; the same as sendfile(Socket, FileHandle, 0, 0, infinity), sendfile(Socket, FileHandle, 0, 0, Timeout), or sendfile(Socket, FileHandle, 0, 0, SelectHandle), that is: send all data in the file to the socket, with the given Timeout.

Link to this function

sendfile(Socket, FileHandle_Cont, Offset, Count)

View Source (since OTP 24.0)
-spec sendfile(socket(), file:fd(), Offset, Count) ->
            {ok, BytesSent} | {error, Reason} | {error, {Reason, BytesSent}}
            when
                Offset :: integer(),
                Count :: non_neg_integer(),
                Reason :: posix() | closed | invalid(),
                BytesSent :: non_neg_integer().

The same as sendfile(Socket, FileHandle, Offset, Count, infinity), that is: send the file data at Offset and Count to the socket, without time-out other than from the platform's network stack.

Link to this function

sendfile/5

View Source (since OTP 24.0)
-spec sendfile(Socket, Cont, Offset, Count, SelectHandle :: nowait) ->
            {ok, BytesSent} |
            {select, SelectInfo} |
            {select, {SelectInfo, BytesSent}} |
            {error, Reason}
            when
                Socket :: socket(),
                Cont :: select_info(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                SelectInfo :: select_info(),
                Reason :: posix() | closed | invalid();
        (Socket, Cont, Offset, Count, SelectHandle :: select_handle()) ->
            {ok, BytesSent} |
            {select, SelectInfo} |
            {select, {SelectInfo, BytesSent}} |
            {error, Reason}
            when
                Socket :: socket(),
                Cont :: select_info(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                SelectInfo :: select_info(),
                Reason :: posix() | closed | invalid();
        (Socket, Cont, Offset, Count, Timeout :: infinity) ->
            {ok, BytesSent} | {error, Reason} | {error, {Reason, BytesSent}}
            when
                Socket :: socket(),
                Cont :: select_info(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                Reason :: posix() | closed | invalid();
        (Socket, Cont, Offset, Count, Timeout :: non_neg_integer()) ->
            {ok, BytesSent} | {error, Reason | timeout} | {error, {Reason | timeout, BytesSent}}
            when
                Socket :: socket(),
                Cont :: select_info(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                Reason :: posix() | closed | invalid();
        (Socket, FileHandle, Offset, Count, SelectHandle :: nowait) ->
            {ok, BytesSent} |
            {select, SelectInfo} |
            {select, {SelectInfo, BytesSent}} |
            {error, Reason}
            when
                Socket :: socket(),
                FileHandle :: file:fd(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                SelectInfo :: select_info(),
                Reason :: posix() | closed | invalid();
        (Socket, FileHandle, Offset, Count, SelectHandle :: select_handle()) ->
            {ok, BytesSent} |
            {select, SelectInfo} |
            {select, {SelectInfo, BytesSent}} |
            {error, Reason}
            when
                Socket :: socket(),
                FileHandle :: file:fd(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                SelectInfo :: select_info(),
                Reason :: posix() | closed | invalid();
        (Socket, FileHandle, Offset, Count, Timeout :: infinity) ->
            {ok, BytesSent} | {error, Reason} | {error, {Reason, BytesSent}}
            when
                Socket :: socket(),
                FileHandle :: file:fd(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                Reason :: posix() | closed | invalid();
        (Socket, FileHandle, Offset, Count, Timeout :: non_neg_integer()) ->
            {ok, BytesSent} | {error, Reason | timeout} | {error, {Reason | timeout, BytesSent}}
            when
                Socket :: socket(),
                FileHandle :: file:fd(),
                Offset :: integer(),
                Count :: non_neg_integer(),
                BytesSent :: non_neg_integer(),
                Reason :: posix() | closed | invalid().

Sends file data on a socket, to the specified destination, waiting for it to be sent ("infinite" time-out).

The FileHandle must refer to an open raw file as described in file:open/2.

This call will not return until the data has been accepted by the platform's network layer, or it reports an error.

The Offset argument is the file offset to start reading from. The default value is 0.

The Count argument is the number of bytes to transfer from FileHandle to Socket. If Count =:= 0 (the default) the transfer stops at the end of file.

The return value indicates the result from the platform's network layer:

  • {ok, BytesSent} - The transfer completed successfully after BytesSent bytes of data.

  • {error, Reason} - An error has been reported and no data has been transferred. The posix/0 Reasons are from the platform's network layer. closed means that this socket library knows that the socket is closed, and invalid/0 means that something about an argument is invalid.

  • {error, {Reason, BytesSent}} - An error has been reported but before that some data was transferred. See {error, Reason} and {ok, BytesSent} above.

Sends file data on a socket, waiting at most Timeout milliseconds for it to be sent (limited time-out).

The same as "infinite" time-out sendfile/5 but returns {error, timeout} or {error, {timeout, BytesSent}} after Timeout milliseconds, if not all file data was transferred by the platform's network layer.

Sends file data on a socket, but returns a select continuation if the data could not be sent immediately (nowait).

The same as "infinite" time-out sendfile/5 but if the data is not immediately accepted by the platform network layer, the function returns {select, SelectInfo}, and the caller will then receive a select message, {'$socket', Socket, select, SelectHandle} ( with the SelectHandle that was contained in the SelectInfo ) when there is room for more data. Then a call to sendfile/3 with SelectInfo as the second argument will continue the data transfer.

If SelectHandle is a select_handle/0, that term will be contained in a returned SelectInfo and the corresponding select message. The SelectHandle is presumed to be unique to this call.

If SelectHandle is nowait, and a SelectInfo is returned, it will contain a select_handle() generated by the call.

If some file data was sent, the function will return {ok, {BytesSent, SelectInfo}.If the caller does not want to wait to send the rest of the data, it should immediately cancel the operation with cancel/2.

Continues sending file data on a socket, where the send operation was initiated by sendfile/3,5 that returned a SelectInfo continuation. Otherwise like "infinite" time-out sendfile/5 , limited time-out sendfile/5 or nowait sendfile/5 respectively.

Cont is the SelectInfo that was returned from the previous sendfile() call.

The return value indicates the result from the platform's network layer. See "infinite" time-out sendfile/5.

Link to this function

sendmsg(Socket, Msg)

View Source (since OTP 22.0)
-spec sendmsg(Socket, Msg) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid().

Equivalent to sendmsg/4

Link to this function

sendmsg/3

View Source (since OTP 24.0)
-spec sendmsg(Socket, Msg, Flags) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               Flags :: [msg_flag() | integer()],
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid();
       (Socket, Data, Cont) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Data :: erlang:iovec(),
               Cont :: select_info(),
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Timeout :: nowait) ->
           ok |
           {ok, RestData} |
           {select, SelectInfo} |
           {select, {SelectInfo, RestData}} |
           {completion, CompletionInfo} |
           {error, Reason} |
           {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               RestData :: erlang:iovec(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Handle :: select_handle() | completion_handle()) ->
           ok |
           {ok, RestData} |
           {select, SelectInfo} |
           {select, {SelectInfo, RestData}} |
           {completion, CompletionInfo} |
           {error, Reason} |
           {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               RestData :: erlang:iovec(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Timeout :: infinity) ->
           ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Timeout :: non_neg_integer()) ->
           ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid().

Equivalent to sendmsg/4

Link to this function

sendmsg/4

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec sendmsg(Socket, Msg, Flags, Timeout :: nowait) ->
           ok |
           {ok, RestData} |
           {select, SelectInfo} |
           {select, {SelectInfo, RestData}} |
           {completion, CompletionInfo} |
           {error, Reason} |
           {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               Flags :: [msg_flag() | integer()],
               RestData :: erlang:iovec(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Flags, Handle :: select_handle() | completion_handle()) ->
           ok |
           {ok, RestData} |
           {select, SelectInfo} |
           {select, {SelectInfo, RestData}} |
           {completion, CompletionInfo} |
           {error, Reason} |
           {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               Flags :: [msg_flag() | integer()],
               RestData :: erlang:iovec(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Flags, Timeout :: infinity) ->
           ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               Flags :: [msg_flag() | integer()],
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid();
       (Socket, Msg, Flags, Timeout :: non_neg_integer()) ->
           ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
           when
               Socket :: socket(),
               Msg :: msg_send(),
               Flags :: [msg_flag() | integer()],
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid();
       (Socket, Data, Cont, Timeout :: nowait) ->
           ok |
           {ok, RestData} |
           {select, SelectInfo} |
           {select, {SelectInfo, RestData}} |
           {completion, CompletionInfo} |
           {error, Reason} |
           {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Data :: msg_send() | erlang:iovec(),
               Cont :: select_info(),
               RestData :: erlang:iovec(),
               SelectInfo :: select_info(),
               CompletionInfo :: completion_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Data, Cont, SelectHandle :: select_handle()) ->
           ok |
           {ok, RestData} |
           {select, SelectInfo} |
           {select, {SelectInfo, RestData}} |
           {error, Reason} |
           {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Data :: msg_send() | erlang:iovec(),
               Cont :: select_info(),
               RestData :: erlang:iovec(),
               SelectInfo :: select_info(),
               Reason :: posix() | closed | invalid();
       (Socket, Data, Cont, Timeout :: infinity) ->
           ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
           when
               Socket :: socket(),
               Data :: msg_send() | erlang:iovec(),
               Cont :: select_info(),
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid();
       (Socket, Data, Cont, Timeout :: non_neg_integer()) ->
           ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
           when
               Socket :: socket(),
               Data :: msg_send() | erlang:iovec(),
               Cont :: select_info(),
               RestData :: erlang:iovec(),
               Reason :: posix() | closed | invalid().

Sends a message on a socket, waiting for it to be sent.

The destination, if needed, that is: if the socket is not connected, is provided in Msg, which also contains the data to send as a list of binaries. Msg may also contain an list of optional control messages (depending on what the protocol and platform supports).

For a connected socket no address field should be present in Msg, the platform may return an error or ignore one.

The message data is given to to the platform's network layer in the form of an I/O vector without copying the content. If the number of elements in the I/O vector is larger than allowed on the platform (reported in the iov_max field from info/0), on a socket of type stream the send is iterated over all elements, but for other socket types the call fails.

This call will not return until the data has been handed over to the platform's network layer, or when it reports an error.

The message Flags may be symbolic msg_flag/0s and/or integer/0s, matching the platform's appropriate header files. The values of all symbolic flags and integers are or:ed together.

The return value indicates the result from the platform's network layer. See send/2,3,4.

Note

On Windows, this function can only be used with datagram and raw sockets.

Sends a message on a socket, waiting at most Timeout milliseconds for it to be sent.

The same as infinite time-out sendmsg/2,3,4 but returns {error, timeout} or {error, {timeout, RestData}} after Timeout milliseconds, if no data or only some of it was accepted by the platform's network layer.

Note

On Windows, this function can only be used with datagram and raw sockets.

Sends a message on a socket, but returns completion or a select continuation if the data could not be sent immediately.

The same as infinity time-out sendmsg/2,3 but if the data is not immediately accepted by the platform network layer, the function returns (on Unix) {select, SelectInfo} or (on Windows) {completion, CompletionInfo}, and the caller will then receive one of these messages:

  • select message - {'$socket', Socket, select, SelectHandle} ( with the SelectHandle that was contained in the SelectInfo ) when there is room for more data. A subsequent call to sendmsg/2-4 will then send the data.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the send will be in the CompletionStatus.

If Handle, is a select_handle/0 or completion_handle/0, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding select or completion message. The Handle is presumed to be unique to this call.

If Timeout is nowait, and a SelectInfo or CompletionInfo is returned, it will contain a select_handle/0 or completion_handle/0 generated by the call.

If some of the data was sent, the function will return {select, {RestData, SelectInfo},which can only happen for a socket of type stream. If the caller does not want to wait to send the rest of the data, it should immediately cancel the operation with cancel/2.

Note

On Windows, this function can only be used with datagram and raw sockets.

Continues sending a message data on a socket, where the send operation was initiated by sendmsg/3,4 that returned a SelectInfo continuation. Otherwise like infinite time-out sendmsg/2,3,4 , limited time-out sendmsg/3,4 or nowait sendmsg/3,4 respectively.

Cont is the SelectInfo that was returned from the previous sendmsg() call.

The return value indicates the result from the platform's network layer. See send/2,3,4 and nowait sendmsg/3,4.

Link to this function

sendto(Socket, Data, Dest_Cont)

View Source (since OTP 24.0)
-spec sendto(Socket, Data, Dest) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              RestData :: binary(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Cont) -> ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Cont :: select_info(),
              RestData :: binary(),
              Reason :: posix() | closed | invalid().

Equivalent to sendto/4

Link to this function

sendto/4

View Source (since OTP 24.0)
-spec sendto(Socket, Data, Dest, Flags) ->
          ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              Flags :: [msg_flag() | integer()],
              RestData :: binary(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Handle :: nowait) ->
          ok |
          {ok, RestData} |
          {select, SelectInfo} |
          {select, {SelectInfo, RestData}} |
          {completion, CompletionInfo} |
          {error, Reason}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              RestData :: binary(),
              SelectInfo :: select_info(),
              CompletionInfo :: completion_info(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Handle :: select_handle() | completion_handle()) ->
          ok |
          {ok, RestData} |
          {select, SelectInfo} |
          {select, {SelectInfo, RestData}} |
          {completion, CompletionInfo} |
          {error, Reason}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              RestData :: binary(),
              SelectInfo :: select_info(),
              CompletionInfo :: completion_info(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Timeout :: infinity) ->
          ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              RestData :: binary(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Timeout :: non_neg_integer()) ->
          ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              RestData :: binary(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Cont, SelectHandle :: nowait) ->
          ok |
          {ok, RestData} |
          {select, SelectInfo} |
          {select, {SelectInfo, RestData}} |
          {error, Reason}
          when
              Socket :: socket(),
              Data :: iodata(),
              Cont :: select_info(),
              RestData :: binary(),
              SelectInfo :: select_info(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Cont, SelectHandle :: select_handle()) ->
          ok |
          {ok, RestData} |
          {select, SelectInfo} |
          {select, {SelectInfo, RestData}} |
          {error, Reason}
          when
              Socket :: socket(),
              Data :: iodata(),
              Cont :: select_info(),
              RestData :: binary(),
              SelectInfo :: select_info(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Cont, Timeout :: infinity) ->
          ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Cont :: select_info(),
              RestData :: binary(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Cont, Timeout :: non_neg_integer()) ->
          ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Cont :: select_info(),
              RestData :: binary(),
              Reason :: posix() | closed | invalid().

Continues sending data on a socket, where the send operation was initiated by sendto/4,5 that returned a SelectInfo continuation. Otherwise like infinite time-out sendto/3,4,5 , limited time-out sendto/4,5 or nowait sendto/4,5 respectively.

Cont is the SelectInfo that was returned from the previous sendto() call.

If Data is not a binary/0, it will be copied into one, again.

The return value indicates the result from the platform's network layer. See send/2,3,4 and nowait sendto/4,5.

Link to this function

sendto/5

View Source (since OTP 22.0, OTP 22.1, OTP 24.0)
-spec sendto(Socket, Data, Dest, Flags, Handle :: nowait) ->
          ok |
          {ok, RestData} |
          {select, SelectInfo} |
          {select, {SelectInfo, RestData}} |
          {completion, CompletionInfo} |
          {error, Reason}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              Flags :: [msg_flag() | integer()],
              RestData :: binary(),
              SelectInfo :: select_info(),
              CompletionInfo :: completion_info(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Flags, Handle :: select_handle() | completion_handle()) ->
          ok |
          {ok, RestData} |
          {select, SelectInfo} |
          {select, {SelectInfo, RestData}} |
          {completion, CompletionInfo} |
          {error, Reason}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              Flags :: [msg_flag() | integer()],
              RestData :: binary(),
              SelectInfo :: select_info(),
              CompletionInfo :: completion_info(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Flags, Timeout :: infinity) ->
          ok | {ok, RestData} | {error, Reason} | {error, {Reason, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              Flags :: [msg_flag() | integer()],
              RestData :: binary(),
              Reason :: posix() | closed | invalid();
      (Socket, Data, Dest, Flags, Timeout :: non_neg_integer()) ->
          ok | {ok, RestData} | {error, Reason | timeout} | {error, {Reason | timeout, RestData}}
          when
              Socket :: socket(),
              Data :: iodata(),
              Dest :: sockaddr(),
              Flags :: [msg_flag() | integer()],
              RestData :: binary(),
              Reason :: posix() | closed | invalid().

Sends data on a socket, to the specified destination, waiting for it to be sent.

This call will not return until the data has been accepted by the platform's network layer, or it reports an error.

If this call is used on a connection mode socket or on a connected socket, the platforms's network layer may return an error or ignore the destination address.

The message Flags may be symbolic msg_flag/0s and/or integer/0s, matching the platform's appropriate header files. The values of all symbolic flags and integers are or:ed together.

The return value indicates the result from the platform's network layer. See send/2,3,4.

Sends data on a socket, waiting at most Timeout milliseconds for it to be sent.

The same as infinite time-out sendto/3,4,5 but returns {error, timeout} or {error, {timeout, RestData}} after Timeout milliseconds, if no Data or only some of it was accepted by the platform's network layer.

Sends data on a socket, but returns completion or a select continuation if the data could not be sent immediately.

The same as infinity time-out sendto/3,4 but if the data is not immediately accepted by the platform network layer, the function returns (on Unix) {select, SelectInfo} or (on Windows) {completion, CompletionInfo}, and the caller will then receive one of these messages:

  • select message - {'$socket', Socket, select, SelectHandle} ( with the SelectHandle that was contained in the SelectInfo ) when there is room for more data.

    A subsequent call to send/2-4 will then send the data.

  • completion message - {'$socket', Socket, completion, {CompletionHandle, CompletionStatus}} (with the CompletionHandle contained in the CompletionInfo).

    The result of the send will be in the CompletionStatus.

If Handle is a select_handle/0 or completion_handle/0, that term will be contained in a returned SelectInfo or CompletionInfo and the corresponding select or completion message. The Handle is presumed to be unique to this call.

If Handle is nowait, and a SelectInfo or CompletionInfo is returned, it will contain a select_handle/0 or completion_handle/0 generated by the call.

If some of the data was sent, the function will return {select, {RestData, SelectInfo},which can only happen (on Unix) for a socket of type stream. If the caller does not want to wait to send the rest of the data, it should immediately cancel the operation with cancel/2.

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setopt/3

View Source (since OTP 24.0)
-spec setopt(socket(), SocketOption :: {Level :: otp, Opt :: otp_socket_option()}, _) ->
          ok | {error, invalid() | closed};
      (socket(), SocketOption :: socket_option(), _) -> ok | {error, posix() | invalid() | closed}.

Sets a socket option in the protocol level otp, which is this implementation's level above the OS protocol layers.

See the type otp_socket_option() for a description of the options on this level.

Set a socket option in one of the OS's protocol levels. See the type socket_option/0 for which options that this implementation knows about, how they are related to option names in the OS, and if there are known peculiarities with any of them.

What options are valid depends on what kind of socket it is (domain/0, type/0 and protocol/0).

See the socket options chapter of the users guide for more info.

Note

Not all options are valid, nor possible to set, on all platforms. That is, even if "we" support an option; it does not mean that the underlying OS does.

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setopt/4

View Source (since OTP 22.0)
-spec setopt(socket(), otp | level(), term(), term()) -> ok | {error, posix() | invalid() | closed}.

setopt(Socket, Level, Opt, Value) -> ok | {error, Reason}

Backwards compatibility function.

The same as setopt(Socket, {Level, Opt}, Value)

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setopt_native/3

View Source (since OTP 24.0)
-spec setopt_native(socket(),
              SocketOption ::
                  socket_option() |
                  {Level :: level() | (NativeLevel :: integer()), NativeOpt :: integer()},
              Value :: native_value()) ->
                 ok | {error, posix() | invalid() | closed}.

Sets a socket option that may be unknown to our implementation, or that has a type not compatible with our implementation, that is; in "native mode".

If Value is an integer/0 it will be used as a C type (int), if it is a boolean/0 it will be used as a C type (int) with the C implementations values for false or true, and if it is a binary/0 its content and size will be used as the option value.

The socket option may be specified with an ordinary socket_option() tuple, with a known Level = level() and an integer NativeOpt, or with both an integer NativeLevel and NativeOpt.

What options are valid depends on what kind of socket it is (domain/0, type/0 and protocol/0).

The integer values for NativeLevel and NativeOpt as well as the encoding of Value has to be deduced from the header files for the running system.

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shutdown(Socket, How)

View Source (since OTP 22.0)
-spec shutdown(Socket, How) -> ok | {error, Reason}
            when Socket :: socket(), How :: read | write | read_write, Reason :: posix() | closed.

Shut down all or part of a full-duplex connection.

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sockname(Socket)

View Source (since OTP 22.0)
-spec sockname(Socket) -> {ok, SockAddr} | {error, Reason}
            when Socket :: socket(), SockAddr :: sockaddr_recv(), Reason :: posix() | closed.

Returns the current address to which the socket is bound.

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supports()

View Source (since OTP 22.0)
-spec supports() ->
            [{Key1 :: term(),
              boolean() | [{Key2 :: term(), boolean() | [{Key3 :: term(), boolean()}]}]}].

Equivalent to supports/2

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supports(Key1)

View Source (since OTP 22.0)
-spec supports(Key1 :: term()) -> [{Key2 :: term(), boolean() | [{Key3 :: term(), boolean()}]}].

Equivalent to supports/2

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supports(Key1, Key2)

View Source (since OTP 22.0)
-spec supports(Key1 :: term(), Key2 :: term()) -> [{Key3 :: term(), boolean()}].

These functions function retrieves information about what the platform supports, such which platform features or which socket options, are supported.

For keys other than the known the empty list is returned, Note that in a future version or on a different platform there might be more supported items.

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use_registry(D)

View Source (since OTP 23.1)
-spec use_registry(D :: boolean()) -> ok.

Globally change if the socket registry is to be used or not. Note that its still possible to override this explicitly when creating an individual sockets, see open/2 or open/4 for more info (use the Extra argument).

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which_sockets()

View Source (since OTP 22.3)
-spec which_sockets() -> [socket()].

Equivalent to which_sockets/1

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which_sockets(FilterRule)

View Source (since OTP 22.3)
-spec which_sockets(FilterRule) -> [socket()]
                 when
                     FilterRule ::
                         inet | inet6 | local | stream | dgram | seqpacket | sctp | tcp | udp |
                         pid() |
                         fun((socket_info()) -> boolean()).

Returns a list of all sockets, according to the filter rule.

There are several pre-made filter rule(s) and one general:

  • inet | inet6 - Selection based on the domain of the socket.
    Only a subset is valid.

  • stream | dgram | seqpacket - Selection based on the type of the socket.
    Only a subset is valid.

  • sctp | tcp | udp - Selection based on the protocol of the socket.
    Only a subset is valid.

  • pid/0 - Selection base on which sockets has this pid as Controlling Process.

  • fun((socket_info()) -> boolean()) - The general filter rule.
    A fun that takes the socket info and returns a boolean/0 (true if the socket could be included and false if should not).