PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SOCKET(3P)                POSIX Programmer's Manual               SOCKET(3P)

PROLOG         top

       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         top

       socket — create an endpoint for communication

SYNOPSIS         top

       #include <sys/socket.h>

       int socket(int domain, int type, int protocol);

DESCRIPTION         top

       The socket() function shall create an unbound socket in a
       communications domain, and return a file descriptor that can be used
       in later function calls that operate on sockets.

       The socket() function takes the following arguments:

       domain      Specifies the communications domain in which a socket is
                   to be created.

       type        Specifies the type of socket to be created.

       protocol    Specifies a particular protocol to be used with the
                   socket. Specifying a protocol of 0 causes socket() to use
                   an unspecified default protocol appropriate for the
                   requested socket type.

       The domain argument specifies the address family used in the
       communications domain. The address families supported by the system
       are implementation-defined.

       Symbolic constants that can be used for the domain argument are
       defined in the <sys/socket.h> header.

       The type argument specifies the socket type, which determines the
       semantics of communication 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
       socket() function or to create some sockets.

RETURN VALUE         top

       Upon successful completion, socket() shall return a non-negative
       integer, the socket file descriptor.  Otherwise, a value of −1 shall
       be returned and errno set to indicate the error.

ERRORS         top

       The socket() function shall fail if:

       EAFNOSUPPORT
              The implementation does not support the specified address
              family.

       EMFILE All file descriptors available to the process are currently
              open.

       ENFILE No more file descriptors are available for the system.

       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 socket() 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         top

       None.

APPLICATION USAGE         top

       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 application can determine whether an address family is supported
       by trying to create a socket with domain set to the protocol in
       question.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       accept(3p), bind(3p), connect(3p), getsockname(3p), getsockopt(3p),
       listen(3p), recv(3p), recvfrom(3p), recvmsg(3p), send(3p),
       sendmsg(3p), setsockopt(3p), shutdown(3p), socketpair(3p)

       The Base Definitions volume of POSIX.1‐2008, netinet_in.h(0p),
       sys_socket.h(0p)

COPYRIGHT         top

       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 .

IEEE/The Open Group                 2013                          SOCKET(3P)