Me and my friend bought this on steam today and we cannot play online. Whenever we create a game, it will show in the server list but we are unable to click on the join ****on. The ****on is greyed out.
We tried using hamachi but the game wont even show up in the lan section.
I don't play on-line but maybe someone that has will better answer your question then I do.
There is another site that offers on-line play, called Tunngle
You might want to give that a try.
Hope things work out. I do know if you play on-line you have to have the same mods, etc that the other players do. At least that is how it use to be.