I've been learning more about Multiplayer game architecture this weekend. There are amazing resources out there, and I've been learning as much as I can about client-side prediction, physics state synchronization, packet compression, and other techniques. But there's something super basic I don't know, which I've had trouble finding info about: In an authoritative server setup, how does a client actually start an instance of the sim server? I assume there aren't servers always running, destroying some company's energy bill. So does he client call a php (or other) script on the server machine which starts a sim server with some initial parameters? I'm pretty sure I'm talking dumb , so if anyone would explain how this works, I'd be forever grateful.