.\" Copyright (c) 1983, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)socketpair.2	6.4 (Berkeley) 03/10/91
.\"
.Dd 
.Dt SOCKETPAIR 2
.Os BSD 4.2
.Sh NAME
.Nm socketpair
.Nd create a pair of connected sockets
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/socket.h>
.Ft int
.Fn socketpair "int d" "int type" "int protocol" "int *sv"
.Sh DESCRIPTION
The
.Fn socketpair
call creates an unnamed pair of connected sockets in
the specified domain
.Fa d ,
of the specified
.Fa type ,
and using the optionally specified
.Fa protocol .
The descriptors used in referencing the new sockets
are returned in
.Fa sv Ns [0]
and
.Fa sv Ns [1] .
The two sockets are indistinguishable.
.Sh DIAGNOSTICS
A 0 is returned if the call succeeds, -1 if it fails.
.Sh ERRORS
The call succeeds unless:
.Bl -tag -width EPROTONOSUPPORTA
.It Bq Er EMFILE
Too many descriptors are in use by this process.
.It Bq Er EAFNOSUPPORT
The specified address family is not supported on this machine.
.It Bq Er EPROTONOSUPPORT
The specified protocol is not supported on this machine.
.It Bq Er EOPNOSUPPORT
The specified protocol does not support creation of socket pairs.
.It Bq Er EFAULT
The address
.Fa sv
does not specify a valid part of the
process address space.
.Sh SEE ALSO
.Xr read 2 ,
.Xr write 2 ,
.Xr pipe 2
.Sh BUGS
This call is currently implemented only for the
.Tn UNIX
domain.
.Sh HISTORY
The
.Nm
function call appeared in
.Bx 4.2 .