socketpair(3p) — Linux manual 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
       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 file descriptors
       shall be allocated as described in Section 2.14, File Descriptor
       Allocation.

       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, no file descriptors shall be allocated, and the contents
       of socket_vector shall be left unmodified.

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

       Section 2.14, File Descriptor Allocation, socket(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_socket.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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 .

IEEE/The Open Group               2017                    SOCKETPAIR(3P)

Pages that refer to this page: sys_socket.h(0p), sys_un.h(0p), socket(3p)

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