Multiplayer Game Server


Difficulty	Advanced
Team Size	3-5 people
Time	~35-45 hours
Demo-ready by	Step 5
Prerequisites	Node.js, WebSocket, game loop concepts
Built by	Photon Engine, Colyseus, PlayFab, Nakama

Skills you'll earn: Authoritative game state, latency compensation, matchmaking algorithms, lobby systems, tick-based simulation

Start by syncing two players' positions over a socket. End with a game server handling lobbies, matchmaking, authoritative state, and latency compensation.

Step 1: Sync player positions (~2-3 hours)

Two players in a shared space. Each should see the other move.

Build a WebSocket server that accepts connections
Client sends its position { x, y } on every frame (or throttled to 20 times/sec)
Server broadcasts each player's position to all others
Render all players on a Canvas — your player in one color, others in another

You now have: Two-player position sync.

Step 2: Authoritative server (~3-4 hours)

Trusting the client means anyone can teleport by sending fake positions.

Server owns the game state: all player positions, velocities, and health
Clients send inputs (key presses), not positions
Server applies inputs to the game state using fixed-tick simulation (e.g., 60 ticks/sec)
Server broadcasts the authoritative state to all clients

You now have: Cheat-resistant game state.

Step 3: Client-side prediction and reconciliation (~3-4 hours)

Waiting for the server to confirm every input feels laggy.

Client predicts the result of its own inputs immediately (move locally)
When the server state arrives, compare with prediction
If they differ, snap to the server state and re-apply unacknowledged inputs
This is client-side prediction — the standard netcode pattern

You now have: Responsive controls with server authority.

Step 4: Lobbies and rooms (~4-5 hours)

All players in one game doesn't scale.

Add lobby management: create room, join room, list rooms
Each room runs an independent game loop
Limit players per room (e.g., 4-8)
Show a lobby browser UI before joining a game

You now have: Multi-room game sessions.

Step 5: Matchmaking (~4-5 hours)

Manual room selection is tedious for competitive games.

Players join a matchmaking queue with their skill rating
Matchmaker groups players of similar skill
Create a room, assign matched players, start the game
Expand skill range over time if no match is found (to avoid infinite queues)

You now have: Automatic matchmaking.

Step 6: Lag compensation (~3-4 hours)

Players with high latency hit targets that have already moved on the server.

Server keeps a history of game states (last N ticks)
On a hit-check, rewind state to the shooter's perceived time (current time - their latency)
Validate the hit against the rewound state
This is server-side rewind, the standard FPS netcode technique

Step 7: Game events and spectating (~4-5 hours)

Broadcast game events: kills, scores, power-up pickups
Spectator mode: connect to a room as a viewer, receive state but send no inputs
Post-game summary: stats, timeline of events

Useful Resources

Where to go from here

UDP transport (WebRTC DataChannels for lower latency)
Anti-cheat (server-side validation of impossible movements)
Replay system (record and playback matches)
Leaderboards and ranked seasons
Horizontal scaling (multiple server processes, shard by region)

Multiplayer Game Server ​

Step 1: Sync player positions (~2-3 hours) ​

Step 2: Authoritative server (~3-4 hours) ​

Step 3: Client-side prediction and reconciliation (~3-4 hours) ​

Step 4: Lobbies and rooms (~4-5 hours) ​

Step 5: Matchmaking (~4-5 hours) ​

Step 6: Lag compensation (~3-4 hours) ​

Step 7: Game events and spectating (~4-5 hours) ​

Useful Resources ​

Where to go from here ​