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socketpair(2)


NAME

   socketpair - create a pair of connected sockets

SYNOPSIS

   #include <sys/types.h>          /* See NOTES */
   #include <sys/socket.h>

   int socketpair(int domain, int type, int protocol, int sv[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, and errno is
   set appropriately.

   On Linux (and other  systems),  socketpair()  does  not  modify  sv  on
   failure.   A  requirement  standardizing  this  behavior  was  added in
   POSIX.1-2016.

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.

CONFORMING TO

   POSIX.1-2001, POSIX.1-2008, 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).

NOTES

   On Linux, the only supported  domain  for  this  call  is  AF_UNIX  (or
   synonymously,   AF_LOCAL).    (Most   implementations   have  the  same
   restriction.)

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

   POSIX.1  does  not  require  the  inclusion  of <sys/types.h>, and this
   header file is not required on Linux.  However, some  historical  (BSD)
   implementations  required  this  header file, and portable applications
   are probably wise to include it.

SEE ALSO

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

COLOPHON

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.



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