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

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 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.

       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 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 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 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  ques-
       tion.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       accept()  ,  bind() , connect() , getsockname() , getsockopt() , listen() , recv() , recvfrom() , recvmsg() , send() , sendmsg() , setsock-
       opt() , shutdown() , socketpair() , the Base Definitions volume of IEEE Std 1003.1-2001, <netinet/in.h>, <sys/socket.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .

IEEE
/The Open Group						       2003								 SOCKET(P)