SOCKETPAIR
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
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.
NAME
socketpair
--- create a pair of connected sockets
SYNOPSIS
#include <sys/socket.h>
int socketpair(int domain, int type, int protocol,
int socket_vector[2]);
DESCRIPTION
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[0]
and
socket_vector[1].
The file descriptors shall be allocated as described in
Section 2.14,
File Descriptor Allocation.
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.
- socket_vector
-
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 types:
- 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.
- SOCK_SEQPACKET
-
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-defined.
The process may need to have appropriate privileges to use the
socketpair()
function or to create some sockets.
RETURN VALUE
Upon successful completion, this function shall return 0; otherwise,
-1 shall be returned and
errno
set to indicate the error, no file descriptors shall be allocated,
and the contents of
socket_vector
shall be left unmodified.
ERRORS
The
socketpair()
function shall fail if:
- EAFNOSUPPORT
-
The implementation does not support the specified address family.
- 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.
- EOPNOTSUPP
-
The specified protocol does not permit creation of socket pairs.
- EPROTONOSUPPORT
-
The protocol is not supported by the address family, or the protocol is
not supported by the implementation.
- EPROTOTYPE
-
The socket type is not supported by the protocol.
The
socketpair()
function may fail if:
- EACCES
-
The process does not have appropriate privileges.
- ENOBUFS
-
Insufficient resources were available in the system to perform the
operation.
- ENOMEM
-
Insufficient memory was available to fulfill the request.
The following sections are informative.
EXAMPLES
None.
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.
The
socketpair()
function is used primarily with UNIX domain sockets and need not be
supported for other domains.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.14,
File Descriptor Allocation,
socket()
The Base Definitions volume of POSIX.1-2017,
<sys_socket.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
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.opengroup.org/unix/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 .