Listen block

The listen block defines the TCP/IP ports that the IRCd will listen on.

Syntax
listen { ip ; port ; options { ;		 ;		...	}; };

ip
Simply set ip to * (an asterisk) to bind to all available IP's on the machine, OR specify an IP to only bind to that IP address (this latter is usually required at shell providers).

port
This is the port you want to listen on, like 6667. You can also specify a port range, like 6667-6669.

options block (optional)
You can specify options for the port. Valid options are:
 * ssl: TLS/SSL encrypted port
 * clientsonly: port is only for clients
 * serversonly: port is only for servers

Example
listen { ip *; port 6667; };

listen { ip *; port 6697; options { ssl; }; };