socket

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.

The same as accept/1 but returns promptly.

When there is no pending connection to return, 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 a client connects. A subsequent call to accept/1,2 will then return the socket.

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.

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)

Cancel an asynchronous request.

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

Closes the socket.

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.

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

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.

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 succesful 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.

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() for which options that this implementation knows about, how they are related to option names in the OS, and if there are known pecularities with any of them.

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

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

Types

Backwards compatibility function.

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

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() that will contain the fetched option value, or by specifying a binary() 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().

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() according to the C implementation.

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

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.

Get miscellaneous info about the socket library.

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

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.

This function retreives 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).

Listen for connections on a socket.

Returns the number of active sockets.

Create 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 in those cases it expects it 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.

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.

Creates an endpoint (socket) for communication.

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

For some Types there is a default protocol, indicated by default, which it may be possible to specify. And for Domain = local, if a protocol is specified, it must be default.

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.

Returns the address of the peer connected to the socket.

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()s and/or integer()s, 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 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 not be delivered immediately, the function returns {select, SelectInfo}, and the caller will then receive a select message, {'$socket', Socket, select, SelectHandle} ( with the SelectHandle contained in the SelectInfo ) when data has arrived. A subsequent call to recv/1,2,3,4 will then return the data.

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.

Note that for a socket of type stream, 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 call cancel/2 to cancel the operation.

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()s and/or integer()s, 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 if no message could be returned immediately.

The same as infinite time-out recvfrom/1,2,3,4 but if no message can not delivered immediately, the function returns {select, SelectInfo}, and the caller will then receive a select message, {'$socket', Socket, select, SelectHandle} ( with the SelectHandle contained in the SelectInfo ) when data has arrived. A subsequent call to recvfrom/1,2,3,4 will then return the message.

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.

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()s and/or integer()s, 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 if no message could be returned immediately.

The same as infinite time-out recvfrom/1,2,3,4 but if no message can not delivered immediately, the function returns {select, SelectInfo}, and the caller will then receive a select message, {'$socket', Socket, select, SelectHandle} ( with the SelectHandle contained in the SelectInfo ) when data has arrived. A subsequent call to recvmsg/1,2,3,4,5 will then return the data.

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.

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()s and/or integer()s, 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(), 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 can not happen for a socket of type stream where a partially succesful 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 can not 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() Reasons are from the platform's network layer. closed means that this socket library knows that the socket is closed, and invalid() 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 succesful send is retried untill 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 return 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 {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. A subsequent call to send/2-4 will then send the data.

If SelectHandle is a select_handle(), 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 of the data was sent, the function will return {ok, {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 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(), 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.

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()s and/or integer()s, 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 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.

Sends a message on a socket, but return 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 {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. A subsequent call to sendmsg/2-4 will then send the data.

If SelectHandle, is a select_handle(), 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 of the data was sent, the function will return {ok, {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 cancel the operation with cancel/2.

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.

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()s and/or integer()s, 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 return 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 be 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. A subsequent call to sendto/3-5 will then send the data.

If SelectHandle is a select_handle(), 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 of the data was sent, the function will return {ok, {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 cancel the operation with cancel/2.

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(), 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.

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() for which options that this implementation knows about, how they are related to option names in the OS, and if there are known pecularities with any of them.

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

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

Types

Backwards compatibility function.

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

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() it will be used as a C type (int), if it is a boolean() it will be used as a C type (int) with the C implementations values for false or true, and if it is a binary() 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(), type() and protocol()).

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.

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

Returns the current address to which the socket is bound.

These functions function retreives 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.

supports()

Returns a list of {Key1, supports(Key1)} tuples for every Key1 described in supports/1 and {Key1, boolean()} tuples for each of the following keys:

sctp

SCTP support

ipv6

IPv6 support

local

Unix Domain sockets support (AF_UNIX | AF_LOCAL)

netns

Network Namespaces support (Linux, setns(2))

supports(msg_flags = Key1)

Returns a list of {Flag, boolean()} tuples for every Flag in msg_flag() with the boolean() indicating if the flag is supported on this platform.

supports(protocols = Key1)

Returns a list of {Name :: atom(), boolean()} tuples for every Name in protocol() with the boolean() indicating if the protocol is supported on this platform.

supports(options = Key1)

Returns a list of {SocketOption, boolean()} tuples for every SocketOption in socket_option() with the boolean() indicating if the socket option is supported on this platform.

supports(options = Key1, Key2)

For a Key2 in level() returns a list of {Opt, boolean()} tuples for all known socket options Opt on that Level =:= Key2, and the boolean() indicating if the socket option is supported on this platform. See setopt/3 and getopt/2.