ultrix man page for socketpair

socketpair(2)							System Calls Manual						     socketpair(2)

Name
       socketpair - create a pair of connected sockets

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

       socketpair(d, type, protocol, sv)
       int d, type, protocol;
       int sv[2];

Description
       The  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.

Return Values
       A zero (0) is returned if the call succeeds, -1 if it fails.

Diagnostics
       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.

       [EOPNOSUPPORT]	   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), write(2)

																     socketpair(2)