# $EPIC: listen.txt,v 1.3 2006/08/29 18:22:56 sthalik Exp $
======Synopsis:======
$__listen__() \\
$__listen__(<port> [family])

======Technical:======
   * The __listen__ function establishes a passive TCP connection (``server'').
   * The <port> argument is optional and if provided is taken as a number.
   * If the <port> argument is not a number, the empty string is returned.
   * If the <port> argument is not zero and less than 1024, the empty string is returned.
   * The optional family argument can be 4, 6, v4, or v6, and tells the client whether it should bind to IPv4 or IPv6.
   * If the requested port is not available (probably because it is in use by someone else), an error is output and the empty string is returned.
   * The return value is the local port number associated with the connection.

======Practical:======
If you want your script to act as an Internet server, the $listen()
function lets you establish a place where others can $[[connect
function|connect]]() to you.  Once they $[[connect function|connect]]()
to you, you are given a small integer that acts in the same way that
$[[connect function|connect]]() return values do.

======Returns:======
The port number being listened on, or the empty string on error.

======Examples:======
<file>
$listen(1025)             returns 1025
$listen(1023)             error, returns nothing
$listen(0)                returns a system-allocated port number
$listen()                 returns a system-allocated port number
</file>

======History:======
This function first appeared in ircII-2.2pre3