socketpair(2) [debian man page]

SOCKETPAIR(2)						     Linux Programmer's Manual						     SOCKETPAIR(2)

NAME

       socketpair - create a pair of connected sockets

SYNOPSIS

       #include <sys/types.h>	       /* See NOTES */
       #include <sys/socket.h>

       int socketpair(int domain, int type, int protocol, int sv[2]);

DESCRIPTION

       The socketpair() call creates an unnamed pair of connected sockets in the specified domain, of the specified type, and using the optionally
       specified protocol.  For further details of these arguments, see socket(2).

       The descriptors used in referencing the new sockets are returned in sv[0] and sv[1].  The two sockets are indistinguishable.

RETURN VALUE

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS

       EAFNOSUPPORT
	      The specified address family is not supported on this machine.

       EFAULT The address sv does not specify a valid part of the process address space.

       EMFILE Too many descriptors are in use by this process.

       ENFILE The system limit on the total number of open files has been reached.

       EOPNOTSUPP
	      The specified protocol does not support creation of socket pairs.

       EPROTONOSUPPORT
	      The specified protocol is not supported on this machine.

CONFORMING TO

       4.4BSD, POSIX.1-2001.  The socketpair() function call appeared in 4.2BSD.  It is generally  portable  to/from  non-BSD  systems	supporting
       clones of the BSD socket layer (including System V variants).

NOTES

       On  Linux,  the	only  supported domain for this call is AF_UNIX (or synonymously, AF_LOCAL).  (Most implementations have the same restric-
       tion.)

       Since Linux 2.6.27, socketpair() supports the SOCK_NONBLOCK and SOCK_CLOEXEC flags described in socket(2).

       POSIX.1-2001 does not require the inclusion of <sys/types.h>, and this header file is not required  on  Linux.	However,  some	historical
       (BSD) implementations required this header file, and portable applications are probably wise to include it.

SEE ALSO

       pipe(2), read(2), socket(2), write(2), socket(7), unix(7)

COLOPHON

       This  page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-10-11							     SOCKETPAIR(2)

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)