focal (3) socketpair.3posix.gz

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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 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 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.


EXAMPLES
       None.


APPLICATION USAGE
       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.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       socket()

       The Base Definitions volume of POSIX.1‐2008, <sys_socket.h>


       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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .