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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  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 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 sock-
                   ets.  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  mecha-
                     nism for out-of-band data.
       SOCK_DGRAM    Provides  datagrams, which are connectionless-mode, unre-
                     liable 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 socket-
       pair() 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 fam-
              ily.
       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 pro-
              tocol 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 proto-
       cols 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 POSIX.1-2008, <sys_socket.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                       SOCKETPAIR(3P)