The more I read about this game the more it sounds like it could be what Im looking for at the moment.  I think Im going to pick it up. Been watching twitch streams, seems good fun but I think it’s still wanted expensive for me.

In order to host a multiplayer session (either in the game client or the standalone server) you need to have some ports open on your router and fowarded to the IP of the computer hosting the game. The ports which need opening are :
UDP/TCP: 27015
UDP: 27016
UDP: 33540
(this worked for me, there is a few conflicting articles about which ports).