Croteam has issued a small fix for the Serious Sam II demo which fixes the problem that was stopping most people from playing online. If server was not behind a NAT, or was behind a non-strict NAT, client would get the message "Game session is no longer available" when trying to join the game. The patch contains two dlls that need to be replaced for this to work. At least the client needs to be patched and the patched client should be able to connect even to unpatched servers. Thanks: Seriously!

Serious Sam Demo Quick Fix (1.47MB)