socketpair(2)

NAME#

socketpair - create a pair of connected sockets

LIBRARY#

Standard C library (libc, -lc)

SYNOPSIS#

#include <sys/socket.h>

int socketpair(int \ndomain\n, int \ntype\n, int \nprotocol\n, int \nsv\n[2]);

DESCRIPTION#

The socketpair() call creates an unnamed pair of connected sockets in the specified domain, of the specified type, and using the optionally specified protocol. For further details of these arguments, see socket(2).

The file descriptors used in referencing the new sockets are returned in sv[0] and sv[1]. The two sockets are indistinguishable.

RETURN VALUE#

On success, zero is returned. On error, -1 is returned, errno is set to indicate the error, and sv is left unchanged

On Linux (and other systems), socketpair() does not modify sv on failure. A requirement standardizing this behavior was added in POSIX.1-2008 TC2.

ERRORS#

EAFNOSUPPORT

The specified address family is not supported on this machine.

EFAULT

The address sv does not specify a valid part of the process address space.

EMFILE

The per-process limit on the number of open file descriptors has been reached.

ENFILE

The system-wide limit on the total number of open files has been reached.

EOPNOTSUPP

The specified protocol does not support creation of socket pairs.

EPROTONOSUPPORT

The specified protocol is not supported on this machine.

VERSIONS#

On Linux, the only supported domains for this call are AF_UNIX (or synonymously, AF_LOCAL) and AF_TIPC (since Linux 4.12).

STANDARDS#

POSIX.1-2008.

HISTORY#

POSIX.1-2001, 4.4BSD.

socketpair() first appeared in 4.2BSD. It is generally portable to/from non-BSD systems supporting clones of the BSD socket layer (including System V variants).

Since Linux 2.6.27, socketpair() supports the SOCK_NONBLOCK and SOCK_CLOEXEC flags in the type argument, as described in socket(2).

SEE ALSO#

pipe(2), read(2), socket(2), write(2), socket(7), unix(7)