How a real-time multiplayer game stays consistent across the internet despite latency and loss. Multiplayer architectures and the authoritative server, the server tick loop, replicating world state with snapshots and delta compression, client-side prediction and reconciliation, interpolation and lag compensation, tight serialization, and scaling with matchmaking, dedicated servers, and anti-cheat.
Before you start
This is the heart of server-side game development. Take the Network Programming course first (UDP, sockets), and the Client Side Game Developer roadmap for the game loop and physics these systems replicate.
Multiplayer Architectures
The first decision in any multiplayer game: how are clients connected? Peer-to-peer, client-server, and — the standard for competitive games — the authoritative server that owns the truth.
The Authoritative Server Loop
The server runs the game as a fixed-rate simulation: gather inputs, advance the world one tick, broadcast the new state. Learn the tick rate, the fixed timestep, and the input→simulate→send cycle.
State Replication & Snapshots
The server must tell each client what the world looks like — efficiently. Learn snapshots, delta compression against what the client already has, and interest management so you only send what matters.
Client-Side Prediction & Reconciliation
Waiting for the server to confirm every move would feel awful. Client-side prediction makes your own actions instant, and server reconciliation corrects any divergence without a visible jerk.
Interpolation & Lag Compensation
You predict your own character, but other players arrive as delayed snapshots. Entity interpolation makes them move smoothly, and lag compensation makes shooting them fair despite everyone’s latency.
Serialization & Bandwidth
Every byte per packet times every player times every tick adds up fast. Learn to serialize game state compactly — binary formats, bit-packing, and quantization — to fit within a bandwidth budget.
Scaling, Matchmaking & Anti-Cheat
Going from one match to a live service: matchmaking players into sessions, running fleets of dedicated servers, sharding a large world, and stopping cheaters — the operational side of online games.