12 Socket Usage
12.1 Introduction
The socket interface (module) is basically an "thin" layer on top of the OS socket interface. It is assumed that, unless you have special needs, gen_[tcp|udp|sctp] should be sufficent.
Note that just because we have a documented and described option, it does not mean that the OS supports it. So its recommended that the user reads the platform specific documentation for the option used.
12.2 Socket Options
Options for level otp:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| assoc_id | integer() | no | yes | type = seqpacket, protocol = sctp, is an association |
| debug | boolean() | yes | yes | none |
| iow | boolean() | yes | yes | none |
| controlling_process | pid() | yes | yes | none |
| rcvbuf | default | pos_integer() | {pos_integer(), pos_ineteger()} | yes | yes | 'default' only valid for set. The tuple form is only valid for type 'stream' and protocol 'tcp'. |
| rcvctrlbuf | default | pos_integer() | yes | yes | default only valid for set |
| sndctrlbuf | default | pos_integer() | yes | yes | default only valid for set |
| fd | integer() | no | yes | none |
Table 12.1: option levels
Options for level socket:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| acceptcon | boolean() | no | yes | none |
| bindtodevice | string() | yes | yes | none |
| broadcast | boolean() | yes | yes | type = dgram |
| debug | integer() | yes | yes | requires admin capability |
| domain | domain() | no | yes | Not on FreeBSD (for instance) |
| dontroute | boolean() | yes | yes | none |
| keepalive | boolean() | yes | yes | none |
| linger | abort | linger() | yes | yes | none |
| oobinline | boolean() | yes | yes | none |
| peek_off | integer() | yes | yes | domain = local (unix) |
| priority | integer() | yes | yes | none |
| protocol | protocol() | no | yes | none |
| rcvbuf | non_neg_integer() | yes | yes | none |
| rcvlowat | non_neg_integer() | yes | yes | none |
| rcvtimeo | timeval() | yes | yes | none |
| reuseaddr | boolean() | yes | yes | none |
| reuseport | boolean() | yes | yes | domain = inet | inet6 |
| sndbuf | non_neg_integer() | yes | yes | none |
| sndlowat | non_neg_integer() | yes | yes | not changeable on Linux |
| sndtimeo | timeval() | yes | yes | none |
| timestamp | boolean() | yes | yes | none |
| type | type() | no | yes | none |
Table 12.2: socket options
Options for level ip:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| add_membership | ip_mreq() | yes | no | none |
| add_source_membership | ip_mreq_source() | yes | no | none |
| block_source | ip_mreq_source() | yes | no | none |
| drop_membership | ip_mreq() | yes | no | none |
| drop_source_membership | ip_mreq_source() | yes | no | none |
| freebind | boolean() | yes | yes | none |
| hdrincl | boolean() | yes | yes | type = raw |
| minttl | integer() | yes | yes | type = raw |
| msfilter | null | ip_msfilter() | yes | no | none |
| mtu | integer() | no | yes | type = raw |
| mtu_discover | ip_pmtudisc() | yes | yes | none |
| multicast_all | boolean() | yes | yes | none |
| multicast_if | any | ip4_address() | yes | yes | none |
| multicast_loop | boolean() | yes | yes | none |
| multicast_ttl | uint8() | yes | yes | none |
| nodefrag | boolean() | yes | yes | type = raw |
| pktinfo | boolean() | yes | yes | type = dgram |
| recvdstaddr | boolean() | yes | yes | type = dgram |
| recverr | boolean() | yes | yes | none |
| recvif | boolean() | yes | yes | type = dgram | raw |
| recvopts | boolean() | yes | yes | type =/= stream |
| recvorigdstaddr | boolean() | yes | yes | none |
| recvttl | boolean() | yes | yes | type =/= stream |
| retopts | boolean() | yes | yes | type =/= stream |
| router_alert | integer() | yes | yes | type = raw |
| sendsrcaddr | boolean() | yes | yes | none |
| tos | ip_tos() | yes | yes | some high-priority levels may require superuser capability |
| transparent | boolean() | yes | yes | requires admin capability |
| ttl | integer() | yes | yes | none |
| unblock_source | ip_mreq_source() | yes | no | none |
Table 12.3: ip options
Options for level ipv6:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| addrform | inet | yes | no | allowed only for IPv6 sockets that are connected and bound to a v4-mapped-on-v6 address |
| add_membership | ipv6_mreq() | yes | no | none |
| authhdr | boolean() | yes | yes | type = dgram | raw, obsolete? |
| drop_membership | ipv6_mreq() | yes | no | none |
| dstopts | boolean() | yes | yes | type = dgram | raw, requires superuser privileges to update |
| flowinfo | boolean() | yes | yes | type = dgram | raw, requires superuser privileges to update |
| hoplimit | boolean() | yes | yes | type = dgram | raw, requires superuser privileges to update |
| hopopts | boolean() | yes | yes | type = dgram | raw, requires superuser privileges to update |
| mtu | boolean() | yes | yes | Get: Only after the socket has been connected |
| mtu_discover | ipv6_pmtudisc() | yes | yes | none |
| multicast_hops | default | uint8() | yes | yes | none |
| multicast_if | integer() | yes | yes | type = dgram | raw |
| multicast_loop | boolean() | yes | yes | none |
| recverr | boolean() | yes | yes | none |
| recvpktinfo | pktinfo | boolean() | yes | yes | type = dgram | raw |
| router_alert | integer() | yes | yes | type = raw |
| rthdr | boolean() | yes | yes | type = dgram | raw, requires superuser privileges to update |
| unicast_hops | default | uint8() | yes | yes | none |
| v6only | boolean() | yes | no | none |
Table 12.4: ipv6 options
Options for level tcp:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| congestion | string() | yes | yes | none |
| maxseg | integer() | yes | yes | none |
| nodelay | boolean() | yes | yes | none |
Table 12.5: tcp options
Options for level udp:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| cork | boolean() | yes | yes | none |
Table 12.6: udp options
Options for level sctp:
| Option Name | Value Type | Set | Get | Other Requirements and comments |
| associnfo | sctp_assocparams() | yes | yes | none |
| autoclose | non_neg_integer() | yes | yes | none |
| disable_fragments | boolean() | yes | yes | none |
| events | sctp_event_subscribe() | yes | no | none |
| initmsg | sctp_initmsg() | yes | yes | none |
| maxseg | non_neg_integer() | yes | yes | none |
| nodelay | boolean() | yes | yes | none |
| rtoinfo | sctp_rtoinfo() | yes | yes | none |
Table 12.7: sctp options