'\" et

.TH SOCKETPAIR "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

socketpair

\(em create a pair of connected sockets

.SH SYNOPSIS

.LP

.nf

#include <sys/socket.h>

.P

int socketpair(int \fIdomain\fP, int \fItype\fP, int \fIprotocol\fP,

    int \fIsocket_vector\fP[2]);

.fi

.SH DESCRIPTION

The

\fIsocketpair\fR()

function shall create an unbound pair of connected sockets in a

specified

.IR domain ,

of a specified

.IR type ,

under the protocol optionally specified by the

.IR protocol

argument. The two sockets shall be identical. The file descriptors

used in referencing the created sockets shall be returned in

.IR socket_vector [0]

and

.IR socket_vector [1].

.P

The

\fIsocketpair\fR()

function takes the following arguments:

.IP "\fIdomain\fR" 12

Specifies the communications domain in which the sockets are to be

created.

.IP "\fItype\fR" 12

Specifies the type of sockets to be created.

.IP "\fIprotocol\fR" 12

Specifies a particular protocol to be used with the sockets.

Specifying a

.IR protocol

of 0 causes

\fIsocketpair\fR()

to use an unspecified default protocol appropriate for the requested

socket type.

.IP "\fIsocket_vector\fR" 12

Specifies a 2-integer array to hold the file descriptors of the created

socket pair.

.P

The

.IR type

argument specifies the socket type, which determines the semantics of

communications over the socket. The following socket types are defined;

implementations may specify additional socket types:

.IP SOCK_STREAM 14

Provides sequenced, reliable, bidirectional, connection-mode byte

streams, and may provide a transmission mechanism for out-of-band

data.

.IP SOCK_DGRAM 14

Provides datagrams, which are connectionless-mode, unreliable messages

of fixed maximum length.

.IP SOCK_SEQPACKET 14

Provides sequenced, reliable, bidirectional, connection-mode

transmission paths for records. A record can be sent using one or more

output operations and received using one or more input operations, but

a single operation never transfers part of more than one record. Record

boundaries are visible to the receiver via the MSG_EOR flag.

.P

If the

.IR protocol

argument is non-zero, it shall specify a protocol that is supported by

the address family. If the

.IR protocol

argument is zero, the default protocol for this address family and type

shall be used. The protocols supported by the system are

implementation-defined.

.P

The process may need to have appropriate privileges to use the

\fIsocketpair\fR()

function or to create some sockets.

.SH "RETURN VALUE"

Upon successful completion, this function shall return 0; otherwise,

\(mi1 shall be returned and

.IR errno

set to indicate the error.

.SH ERRORS

The

\fIsocketpair\fR()

function shall fail if:

.TP

.BR EAFNOSUPPORT

.br

The implementation does not support the specified address family.

.TP

.BR EMFILE

All, or all but one, of the file descriptors available to the

process are currently open.

.TP

.BR ENFILE

No more file descriptors are available for the system.

.TP

.BR EOPNOTSUPP

The specified protocol does not permit creation of socket pairs.

.TP

.BR EPROTONOSUPPORT

.br

The protocol is not supported by the address family, or the protocol is

not supported by the implementation.

.TP

.BR EPROTOTYPE

The socket type is not supported by the protocol.

.P

The

\fIsocketpair\fR()

function may fail if:

.TP

.BR EACCES

The process does not have appropriate privileges.

.TP

.BR ENOBUFS

Insufficient resources were available in the system to perform the

operation.

.TP

.BR ENOMEM

Insufficient memory was available to fulfill the request.

.LP

.IR "The following sections are informative."

.SH "EXAMPLES"

None.

.SH "APPLICATION USAGE"

The documentation for specific address families specifies which

protocols each address family supports. The documentation for specific

protocols specifies which socket types each protocol supports.

.P

The

\fIsocketpair\fR()

function is used primarily with UNIX domain sockets and need not be

supported for other domains.

.SH "RATIONALE"

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIsocket\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<sys_socket.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.unix.org/online.html .

Any typographical or formatting errors that appear

in this page are most likely

to have been introduced during the conversion of the source files to

man page format. To report such errors, see

https://www.kernel.org/doc/man-pages/reporting_bugs.html .