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.
The socketpair() function shall create an unbound pair of connected
sockets in a specified domain, of a specified type, under the
protocol optionally specified by the protocol argument. The two
sockets shall be identical. The file descriptors used in referencing
the created sockets shall be returned in socket_vector and
The socketpair() function takes the following arguments:
domain Specifies the communications domain in which the sockets
are to be created.
type Specifies the type of sockets to be created.
protocol Specifies a particular protocol to be used with the
sockets. Specifying a protocol of 0 causes socketpair()
to use an unspecified default protocol appropriate for
the requested socket type.
Specifies a 2-integer array to hold the file descriptors
of the created socket pair.
The 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
SOCK_STREAM Provides sequenced, reliable, bidirectional,
connection-mode byte streams, and may provide a
transmission mechanism for out-of-band data.
SOCK_DGRAM Provides datagrams, which are connectionless-mode,
unreliable messages of fixed maximum length.
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.
If the protocol argument is non-zero, it shall specify a protocol
that is supported by the address family. If the protocol argument is
zero, the default protocol for this address family and type shall be
used. The protocols supported by the system are implementation-
The process may need to have appropriate privileges to use the
socketpair() function or to create some sockets.
The socketpair() function shall fail if:
The implementation does not support the specified address
EMFILE All, or all but one, of the file descriptors available to the
process are currently open.
ENFILE No more file descriptors are available for the system.
The specified protocol does not permit creation of socket
The protocol is not supported by the address family, or the
protocol is not supported by the implementation.
The socket type is not supported by the protocol.
The socketpair() function may fail if:
EACCES The process does not have appropriate privileges.
Insufficient resources were available in the system to perform
ENOMEM Insufficient memory was available to fulfill the request.
The following sections are informative.
The documentation for specific address families specifies which
protocols each address family supports. The documentation for
specific protocols specifies which socket types each protocol
The socketpair() function is used primarily with UNIX domain sockets
and need not be supported for other domains.
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
IEEE/The Open Group 2013 SOCKETPAIR(3P)