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



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.


NAME
       socket -- create an endpoint for communication

SYNOPSIS
       #include <sys/socket.h>

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

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

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

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

       The Base Definitions volume of POSIX.1-2008, <netinet_in.h>,
       <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
       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(3)
