over lan clients can connect with any GSTNet server via broadcast (ip=255.255.255.255, same port). no need for a known server ip.
over internet you can use dynamic ip services or GSTNet_Channel, a service script
that uses GSTNet_httpxx functions and a php/sql server on gstools to provide
existing servers and some other info.
http://www.gstools.de/channels/channels.php?gst=ServerList&gui=1