SOCKETPAIR(2)

NAME
socketpair - create a pair of connected sockets

LIBRARY
libc

SYNOPSIS
#include <sys/socket.h>
int
socketpair(int d, int type, int protocol, int *sv);

DESCRIPTION
The socketpair() call creates an unnamed pair of connected sockets in the specified domain d, of the specified type, and using the optionally specified protocol. The descriptors used in referencing the new sockets are returned in sv[0] and sv[1]. The two sockets are indistinguishable.

Possible values for the type argument are SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET; the only supported value for the protocol is 0, which will let the system select an appropriate protocol for the requested socket type.

Any combination of the following flags may additionally be used in the type argument:

SOCK_CLOEXEC
    Set close-on-exec flag on both the new descriptors.
SOCK_CLOFORK
    Set close-on-fork flag on both the new descriptors.
SOCK_NONBLOCK
    Set non-blocking I/O mode on both the new sockets.

RETURN VALUES

ERRORS
The call succeeds unless:

[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]
    Too many descriptors are in use by this process.

[ENFILE]
    The system file table is full.

[EOPNOTSUPP]
    The specified protocol does not support creation of socket pairs.

[EPROTONOSUPPORT]
    The specified protocol is not supported on this machine.

SEE ALSO
close(2), fcntl(2), pipe(2), read(2), socket(2), write(2)

STANDARDS
The socketpair() call conforms to p1003.1-2001. Including the SOCK_CLOEXEC, SOCK_CLOFORK, and SOCK_NONBLOCK flags in the type conforms to p1003.1-2024.

HISTORY
The socketpair() function call appeared in 4.2BSD.

Support for the SOCK_CLOEXEC and SOCK_NONBLOCK flags appeared in NetBSD 6.0.

Support for the SOCK_CLOFORK flag appeared in FreeBSD 15.0, DragonFly 6.5 and NetBSD 11.0.

BUGS
This call is currently implemented only for the PF_LOCAL domain.