socket() -- Sockets Function (libsocket)

Create a socket
#include <sys/types.h>
#include <sys/socket.h>
int socket(domain, type, protocol)
int domain, type, protocol;

socket() creates  a ``socket'' --  that is, an  endpoint for communication.
It returns a descriptor that uniquely identifies the socket.

domain  specifies the  domain within which  communication will  take place.
This selects the protocol family to be used.  These families are defined in
<sys/socket.h> Currently, socket() recognizes the following domains:

AF_UNIX   UNIX internal protocols.
AF_INET   ARPA Internet protocols.

The  socket  has  the indicated  type,  which  specifies  the semantics  of
communication.  socket() recogizes the following types:

SOCK_STREAM
          This  type provides  a byte stream  that is  sequenced, reliable,
          two-way, and connection-based.

SOCK_DGRAM
          This  type  supports ``datagrams''  --  that is,  connectionless,
          unreliable messages of a fixed maximum length.

protocol identifies the protocol to  be used with the newly created socket.
In  most instances,  a given  type  of socket  supports only  one protocol.
However, a socket type may  support many different protocols, in which case
you must specify the one to  use.  The protocol number to use is particular
to the ``communication domain'' in which communication is to take place.

Sockets of type SOCK_STREAM are full-duplex byte streams, similar to pipes.
A stream socket must be in a connected to another socket (through a call to
function connect())  before any data can  be sent to it  or received on it.
Once connected,  data can be transferred using the  system calls read() and
write(). When a session has  been completed, invoke the system call close()
to close the socket.

If  all goes  well, socket()  returns the descriptor  of the  newly created
socket; this  is always  a positive integer.   If something goes  wrong, it
returns -1 and sets errno to an appropriate value.  The following lists the
possible errors, by the value to which socket() sets errno:

EPROTONOSUPPORT
     type or protocol is not supported within this domain.

EMFILE
     The per-process descriptor table is full.

ENFILE
     The system file table is full.

EACCESS
     You  do not  have permission  to create  a socket of  a given  type or
     protocol.

ENOBUFS
     Not enough  buffer space is  available.  The socket  cannot be created
     until sufficient resources are freed.

See Also

accept(),
connect(),
libsocket,
listen(),
read(),
write()

© 2012 by Stephen A. Ness