.\" Copyright (c) 1983, 1991, 1993.\"	The Regents of the University of California.  All rights reserved..\".\" Redistribution and use in source and binary forms, with or without.\" modification, are permitted provided that the following conditions.\" are met:.\" 1. Redistributions of source code must retain the above copyright.\"    notice, this list of conditions and the following disclaimer..\" 2. Redistributions in binary form must reproduce the above copyright.\"    notice, this list of conditions and the following disclaimer in the.\"    documentation and/or other materials provided with the distribution..\" 3. All advertising materials mentioning features or use of this software.\"    must display the following acknowledgement:.\"	This product includes software developed by the University of.\"	California, Berkeley and its contributors..\" 4. Neither the name of the University nor the names of its contributors.\"    may be used to endorse or promote products derived from this software.\"    without specific prior written permission..\".\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION).\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF.\" SUCH DAMAGE..\".\"     @(#)socketpair.2	8.1 (Berkeley) 6/4/93.\".Dd June 4, 1993.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 DESCRIPTIONThe.Fn socketpaircall creates an unnamed pair of connected sockets inthe specified domain.Fa d ,of the specified.Fa type ,and using the optionally specified.Fa protocol .The descriptors used in referencing the new socketsare returned in.Fa sv Ns [0]and.Fa sv Ns [1] .The two sockets are indistinguishable..Sh DIAGNOSTICSA 0 is returned if the call succeeds, -1 if it fails..Sh ERRORSThe call succeeds unless:.Bl -tag -width EPROTONOSUPPORTA.It Bq Er EMFILEToo many descriptors are in use by this process..It Bq Er EAFNOSUPPORTThe specified address family is not supported on this machine..It Bq Er EPROTONOSUPPORTThe specified protocol is not supported on this machine..It Bq Er EOPNOSUPPORTThe specified protocol does not support creation of socket pairs..It Bq Er EFAULTThe address.Fa svdoes not specify a valid part of theprocess address space..Sh SEE ALSO.Xr read 2 ,.Xr write 2 ,.Xr pipe 2.Sh BUGSThis call is currently implemented only for the.Tn UNIXdomain..Sh HISTORYThe.Nmfunction call appeared in.Bx 4.2 .