freebsd man page for socketpair

SOCKETPAIR(2)						      BSD System Calls Manual						     SOCKETPAIR(2)

NAME
     socketpair -- create a pair of connected sockets

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>

     int
     socketpair(int fd, int type, int protocol, int *sv);

DESCRIPTION
     The socketpair() system call creates an unnamed pair of connected sockets in the specified domain fd, 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.

     The SOCK_CLOEXEC and SOCK_NONBLOCK flags in the type argument apply to both descriptors.

RETURN VALUES
     The socketpair() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
     cate the error.

ERRORS
     The call succeeds unless:

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

     [EAFNOSUPPORT]	The specified address family is not supported on this machine.

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

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

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

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

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

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

BSD
								September 11, 2013							       BSD