socket

SYNOPSIS
       #include <sys/socket.h>

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


DESCRIPTION
       The  socket()  function  shall create an unbound socket in a communica-
       tions 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 communica-
       tions  domain.  The address families supported by the system are imple-
       mentation-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.



ERRORS
       The socket() function shall fail if:

       EAFNOSUPPORT

              The  implementation  does not support the specified address fam-
              ily.

       EMFILE No more file descriptors are available for this process.

       ENFILE No more file descriptors are available for the system.

       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 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  proto-
       cols  each address family supports. The documentation for specific pro-
       tocols 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()
       is  the  referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                            SOCKET(P)