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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 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.

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 Too many descriptors are in use by this process.

       ENFILE The  system  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

       4.4BSD,  POSIX.1-2001.   The  socketpair()  function  call  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 described in socket(2).

       POSIX.1-2001 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

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