SOCKETPAIR(P) POSIX Programmer's Manual SOCKETPAIR(P)
socketpair - create a pair of connected sockets
int socketpair(int domain, int type, int protocol,
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 argu-
ment. The two sockets shall be identical. The file descriptors used in referencing the
created sockets shall be returned in socket_vector and socket_vector.
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.
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
The type argument specifies the socket type, which determines the semantics of communica-
tions over the socket. The following socket types are defined; implementations may specify
additional socket types:
Provides sequenced, reliable, bidirectional, connection-mode byte streams, and may
provide a transmission mechanism for out-of-band data.
Provides datagrams, which are connectionless-mode, unreliable messages of fixed
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
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.
Upon successful completion, this function shall return 0; otherwise, -1 shall be returned
and errno set to indicate the error.
The socketpair() function shall fail if:
The implementation does not support the specified address family.
EMFILE No more file descriptors are available for this process.
ENFILE No more file descriptors are available for the system.
The specified protocol does not permit creation of socket pairs.
The protocol is not supported by the address family, or the protocol is not sup-
ported 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 the operation.
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 supports.
The socketpair() function is used primarily with UNIX domain sockets and need not be sup-
ported for other domains.
socket() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/socket.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 SOCKETPAIR(P)