socketpair(2) System Calls Manual socketpair(2)NAME
socketpair - Creates a pair of connected sockets
SYNOPSIS
#include <sys/socket.h>
int socketpair( int domain, int type, int protocol, int socket_vector[2] );
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
socketpair(): XNS5.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies the communications domain in which the sockets are created. This function does not create sockets in the Internet domain. Speci-
fies the communications method that sockets use, for example SOCK_DGRAM or SOCK_STREAM. Specifies an optional identifier used to define
the communications protocols used in the transport layer interface. Specifies a two-integer array used to hold the file descriptors of the
socket pair created with the call to this function.
DESCRIPTION
The socketpair() function creates an unnamed pair of connected sockets in a specified domain, of a specified type, under the protocol
optionally specified by the protocol parameter. The two sockets are identical. The file descriptors used in referencing the created sock-
ets are returned to socket_vector[0] and socket_vector[1]. The sys/socket.h include file contains definitions for socket domains, types,
and protocols.
Not all protocol families support the socketpair() function.
RETURN VALUES
Upon successful completion, this function returns a value of 0 (zero). Otherwise, -1 is returned and errno is specified to indicate the
error.
ERRORS
If the socketpair() function fails, errno may be set to one of the following values: The process have not have appropriate privileges. The
addresses in the specified address family cannot be used to create this socket pair. [Tru64 UNIX] The socket_vector array is not located
in a writable part of user address space. The current process has too many open file descriptors. No more file descriptors are available
for the system. Insufficient resources were available in the system to complete the call. The system was unable to allocate kernel memory
to increase the process descriptor table. The available STREAMS resources were insufficient for the operation to complete. The specified
protocol does not permit creation of socket pairs. The specified protocol cannot be used in this system. The socket type is not supported
by the protocol.
RELATED INFORMATION
Functions: socket(2)
Standards: standards(5) delim off
socketpair(2)
Check Out this Related Man Page
SOCKETPAIR(3P) POSIX Programmer's Manual SOCKETPAIR(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing 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 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.
ERRORS
The socketpair() function shall fail if:
EAFNOSUPPORT
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.
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 pro-
tocols 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
socket(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/socket.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- 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 original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .
IEEE /The Open Group 2003 SOCKETPAIR(3P)