Using examples it shows how to things manually in a low level manner. And then shows how much of the administrative parts of the code can be avoided using the layer2 netchannels ClanLib provides.
Any network game needs to setup the physical connection between server and clients.
A netchannel is analog to a network port. All IP communication is divided into different types, each assigned its own port. HTTP is handled on port 80, FTP on 21, telnet is 23 and so on. The main difference between a netchannel and a IP port is that all netchannels are packed into the same IP port. This is done to allow ClanLib games to be played easily through proxies and firewalls.