PC Cannot join multiplayer games through Steam, or IP

[Freyir]

I cannot join my friend game, as when I do it just stays on the connecting part, without proceding further. The reason for why he has to host the game it's because when I host it, another friend simply cannot stop lagging, but when my other friend host, he doesnt lag anymore (we are a group of 6 in the server)
Any solutions? We are playing with the 1.4.4.9 version