LAN multiplayer feasible?

Okay, I’m kicking around a game idea at the moment that would be way better with multiplayer over a network.

I haven’t found any tutorials on this subject so I’m wondering whether this is something that is considered doable?
Like has it ever been done before or would I have to break new ground to get it working?

Basically there are two fields to watch in reguards to the network gaming. One is the progress of a couple instant messengers that have been written.
The other is the integration Purple into blender.