Kevin Jenkis, author of the network engine
RakNet created a demo which shows how to use Irrlicht and Raknet together to create a multiplayer 3D game.
You can
download the demo here.
Basically, it's the original Irrlicht TechDemo with a multiplayer part added to it. You can run two instances if you want to connect to yourself. The sources can be
downloaded from the sourceforge subversion server.