PLEASE NOTE: The game must be vanilla, most servers do not accept mods. When looking for a server take into consideration the ping and the map. If the map is not familiar to you, avoid it. It is probably a custom made map and it would take a lot of time to download it. Shadow of Chernobyl is still going strong. Here is a quick guide on how to setup your game in case you are having problems with the multiplayer part.
Hide player controls
Hide resume playing