accept

Purpose

     Accepts a connection on a socket.

Library

     Sockets Library (libsock.a)

Syntax

     #include <sys/types.h>
     #include <sys/socket.h>

     int accept (s, addr, addrlen)
     int s;
     struct sockaddr *addr;
     int *addrlen;

Description

     The accept  subroutine extracts  the first  connection on
     the queue  of pending  connections, creates a  new socket
     with the same  properties as s, and allocates  a new file
     descriptor for  that socket.   If no  pending connections
     are present  on the queue  and the calling socket  is not
     marked as non-blocking, accept  blocks the caller until a
     connection is present.   If the socket specified  by s is
     marked non-blocking and there  are no connections pending
     on the queue, accept returns an error as described below.
     The accepted  socket cannot be  used to accept  more con-
     nections.  The  original socket, s, remains  open and can
     accept more connections.

     The s  parameter is  a socket that  was created  with the
     socket subroutine, was bound to  an address with the bind
     subroutine,  and  has issued  a  successful  call to  the
     listen subroutine.

     The addr parameter  is a result parameter  that is filled
     in with the address of the connecting entity, as known to
     the communications  layer.  The  exact format of  addr is
     determined  by  the  domain in  which  the  communication
     occurs.   The addrlen  parameter  initially contains  the
     amount of  space pointed  to by  the addr  parameter.  On
     return, it contains  the actual length (in  bytes) of the
     address   returned.   This   subroutine   is  used   with
     connection-based socket types, such as SOCK_STREAM.

     Before calling the accept subroutine, you can find out if
     the socket is  ready to accept the connection  by doing a
     read select with the select system call.

Return Value

     Upon  successful   completion,  the   nonnegative  socket
     descriptor of  the accepted  socket is returned.   If the
     accept  routine fails,  a value  of -1  is returned,  and
     errno is set to indicate the error.

Diagnostics

     The subroutine fails if one  or more of the following are
     true:

     EBADF             The s parameter is not valid.

     ENOTSOCK          The s parameter refers to a file, not a
                       socket.

     EOPNOTSUPP        The  referenced socket  is not  of type
                       SOCK_STREAM.

     EFAULT            The addr parameter is not in a writable
                       part of the user address space.

     EWOULDBLOCK       The socket is  marked non-blocking, and
                       no  connections   are  present   to  be
                       accepted.

Related Information

     In this  book:    "bind," "connect,"  "listen," "select,"
     and "socket."