DESCRIPTION

     To accept  connections,  a  socket  is  first  created  with
     socket(2),  a willingness to accept incoming connections and
     a queue limit for incoming connections  are  specified  with
     listen,   and   then   the  connections  are  accepted  with
     accept(2).  The listen call applies only to sockets of  type
     SOCK_STREAM or SOCK_SEQPACKET.

     The backlog parameter defines the maximum length  the  queue
     of pending connections may grow to.  If a connection request
     arrives with the queue full the client may receive an  error
     with  an  indication  of ECONNREFUSED, or, if the underlying
     protocol supports retransmission, the request may be ignored
     so that retries may succeed.

RETURN VALUE

     On success, zero is returned.  On error, -1 is returned, and
     errno is set appropriately.

ERRORS

     EBADF   The argument s is not a valid descriptor.

     ENOTSOCK
             The argument s is not a socket.

     EOPNOTSUPP
             The socket is not of a type that supports the opera-
             tion listen.

CONFORMING TO

     SVr4, 4.4BSD (the listen function  call  first  appeared  in
     4.2BSD).

BUGS

     If the socket is of type af_inet, and the  backlog  argument
     is  greater than the constant SO_MAXCONN (128 in 2.0.23), it
     is silently truncated to SO_MAXCONN. For  portable  applica-
     tions  don't rely on this value since BSD (and at least some
     BSD derived systems) limit the backlog to 5.

SEE ALSO

     accept(2), connect(2), socket(2)