Passworded rooms then! Even in games where you play on a centralized server, it’s sometimew possible to have passworded matches. GunZ online comes to mind. I think that game had passworded mqtches. TBF that game had anticheat too, but it never really worked properly. Client side anticheat doesn’t work because someone will always bypass it somehow, and then the server doesn’t know that funny things are happening. And server side anti cheat is going to decrease server performance because you have to track more things in the server and trust the clients less.