PRO/MMO Foundation. Free, open source, multiplayer tools built to scale

Hi, is it possible to do steam login to authorize players into the matchmaking system or should I reject them based on steam auth once they try to reach my game server? This has some issues, as for example, people without the game in their library (pirate versions, for instance) being matched against other players and then not being able to connect leaving the session with fewer players than expected.