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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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SOCKETPAIR(3P) POSIX Programmer's Manual SOCKETPAIR(3P)
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.
socketpair — create a pair of connected sockets
#include <sys/socket.h>
int socketpair(int domain, int type, int protocol,
int socket_vector[2]);
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.
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.
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.
None.
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.
None.
None.
Section 2.14, File Descriptor Allocation, socket(3p)
The Base Definitions volume of POSIX.1‐2017, sys_socket.h(0p)
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 .
IEEE/The Open Group 2017 SOCKETPAIR(3P)
Pages that refer to this page: sys_socket.h(0p), sys_un.h(0p), socket(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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