1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd May 17, 2025 29.Dt SOCKETPAIR 2 30.Os 31.Sh NAME 32.Nm socketpair 33.Nd create a pair of connected sockets 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In sys/types.h 38.In sys/socket.h 39.Ft int 40.Fn socketpair "int domain" "int type" "int protocol" "int *sv" 41.Sh DESCRIPTION 42The 43.Fn socketpair 44system call creates an unnamed pair of connected sockets in 45the specified communications 46.Fa domain , 47of the specified 48.Fa type , 49and using the optionally specified 50.Fa protocol . 51The descriptors used in referencing the new sockets 52are returned in 53.Fa sv Ns [0] 54and 55.Fa sv Ns [1] . 56The two sockets are indistinguishable. 57.Pp 58The 59.Dv SOCK_CLOEXEC , 60.Dv SOCK_CLOFORK 61and 62.Dv SOCK_NONBLOCK 63flags in the 64.Fa type 65argument apply to both descriptors. 66.Sh RETURN VALUES 67.Rv -std socketpair 68.Sh ERRORS 69The call succeeds unless: 70.Bl -tag -width Er 71.It Bq Er EMFILE 72Too many descriptors are in use by this process. 73.It Bq Er EAFNOSUPPORT 74The specified address family is not supported on this machine. 75.It Bq Er EPROTONOSUPPORT 76The specified protocol is not supported on this machine. 77.It Bq Er EOPNOTSUPP 78The specified protocol does not support creation of socket pairs. 79.It Bq Er EFAULT 80The address 81.Fa sv 82does not specify a valid part of the 83process address space. 84.El 85.Sh SEE ALSO 86.Xr pipe 2 , 87.Xr read 2 , 88.Xr socket 2 , 89.Xr write 2 90.Sh STANDARDS 91The 92.Fn socketpair 93system call conforms to 94.St -p1003.1-2001 95and 96.St -p1003.1-2008 . 97.Sh HISTORY 98The 99.Fn socketpair 100system call appeared in 101.Bx 4.2 . 102.Sh BUGS 103This call is currently implemented only for the 104.Ux 105domain. 106