dev-multiplayer-colyseus-server

name	dev-multiplayer-colyseus-server
description	Colyseus server setup, room handlers, lifecycle events, and scaling. Use when setting up multiplayer server.
category	multiplayer

Colyseus Server Setup

Node.js multiplayer framework - authoritative game server with real-time state sync.

When to Use

Use when:

• Setting up Colyseus server
• Creating room handlers
• Implementing matchmaking
• Configuring server transport

Server Setup (ESM Required)

// server/index.ts - MUST use ESM
import { Server } from 'colyseus';
import { createServer } from 'http';
import express from 'express';
import { WebSocketTransport } from '@colyseus/ws-transport';
import { GameRoom } from './rooms/GameRoom';

const port = Number(process.env.PORT) || 2567;

const app = express();

// CORS middleware
app.use((req, res, next) => {
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');
  if (req.method === 'OPTIONS') {
    res.writeHead(200);
    res.end();
    return;
  }
  next();
});

const httpServer = createServer(app);

const gameServer = new Server({
  transport: new WebSocketTransport({ server: httpServer }),
});

gameServer.define('game_room', GameRoom);
gameServer.listen(port);

console.log(`Colyseus server listening on wss://localhost:${port}`);

CRITICAL: Server MUST use "type": "module" in package.json. Do NOT use CommonJS.

Room Handler Definition

import { Room, Client } from 'colyseus';
import { Schema, type, MapSchema } from '@colyseus/schema';

export class GameRoom extends Room<GameRoomState> {
  onCreate(options: any) {
    this.setState(new GameRoomState());
    console.log(`[GameRoom] Created: ${this.roomId}`);

    // Simulation tick (deltaTime in seconds)
    this.setSimulationInterval((deltaTime) => {
      this.update(deltaTime);
    });

    // One-time event
    this.clock.setTimeout(() => this.endMatch(), 5000);

    // Repeated event
    this.clock.setInterval(() => this.checkCondition(), 100);
  }

  onJoin(client: Client, options: any) {
    const player = new PlayerState();
    player.clientId = client.sessionId;
    this.state.players.set(client.sessionId, player);

    client.send('welcome', { playerId: client.sessionId });
  }

  onLeave(client: Client, consented: boolean) {
    this.state.players.delete(client.sessionId);
  }

  onMessage(client: Client, data: any) {
    switch (data.type) {
      case 'player_input':
        this.handleInput(client, data);
        break;
    }
  }

  onDispose() {
    console.log(`[GameRoom] Disposed: ${this.roomId}`);
  }
}

Message Broadcasting

// Broadcast to all clients
this.broadcast('game_event', { data: 'value' });

// Send to specific client
client.send('personal_event', { data: 'value' });

// Send to all except sender
this.broadcast('game_event', { data: 'value' }, [client.sessionId]);

Server Definition Options

// Filter rooms by options for matchmaking
gameServer
  .define('battle', BattleRoom)
  .filterBy(['mode', 'map']);

// Sort rooms for matchmaking priority
gameServer
  .define('battle', BattleRoom)
  .sortBy({ clients: -1 });  // Most players first

// Enable realtime listing
gameServer
  .define('battle', BattleRoom)
  .enableRealtimeListing();

// Listen to lifecycle events
gameServer
  .define('chat', ChatRoom)
  .on('create', (room) => console.log('Room created'))
  .on('dispose', (room) => console.log('Room disposed'))
  .on('join', (room, client) => console.log('Client joined'))
  .on('leave', (room, client) => console.log('Client left'));

Transport Configuration

import { WebSocketTransport } from '@colyseus/ws-transport';

new WebSocketTransport({
  server,                // HTTP server instance
  pingInterval: 30000,    // Ping interval (ms)
  pingMaxRetries: 3,      // Max retries before disconnect
});

// Development: simulate latency
if (process.env.NODE_ENV !== 'production') {
  gameServer.simulateLatency(200);
}

Scaling with Redis

import { Server, RedisPresence, RedisDriver } from 'colyseus';

const gameServer = new Server({
  presence: new RedisPresence(),  // Multi-process communication
  driver: new RedisDriver(),       // Room storage across processes
});

Best Practices

1. Always use ESM - "type": "module" in package.json
2. Validate all inputs - Never trust client data
3. Rate limit actions - Prevent spam exploits
4. Log room lifecycle - For debugging
5. Use Schema for state - Efficient binary serialization

Common Mistakes

❌ Wrong	✅ Right
require/module.exports	import/export with "type": "module"
Server using colyseus.js	Server uses colyseus package
Trusting client positions	Validate all inputs server-side

Reference

• Colyseus Server Docs
• Room Handlers

---

Room Lifecycle Best Practices (Updated 2026-01-28)

From arch-003 retrospective - proven patterns for Colyseus room implementation.

Lifecycle Event Order

onCreate (once) → onAuth (per client) → onJoin (per client) → onMessage (loop)
→ onLeave (per client) → onDispose (once, when no clients)

onCreate Implementation Pattern

import { Room, Client } from 'colyseus';
import { MyRoomState } from '../schema/MyRoomState';

export class MyRoom extends Room<MyRoomState> {
  maxClients = 64;  // Set on class for 64-player FFA

  onCreate(options: any) {
    // 1. Initialize state
    this.setState(new MyRoomState());

    // 2. Set patch rate (20Hz = 50ms for multiplayer games)
    this.setPatchRate(50);  // 50ms = 20 ticks/sec

    // 3. Set up simulation interval (optional game loop)
    this.setSimulationInterval((deltaTime) => {
      this.gameLoop(deltaTime);
    });

    // 4. Register message handlers
    this.onMessage('input', (client, data) => {
      this.handlePlayerInput(client, data);
    });

    console.log(`[Room ${this.roomId}] Created with options:`, options);
  }

  onAuth(client: Client, options: any): boolean | Promise<any> {
    // Return true to allow, false/error to reject
    // Can return Promise for async validation
    return true;
  }

  onJoin(client: Client, options: any) {
    console.log(`[Room ${this.roomId}] Client joined: ${client.sessionId}`);

    // Create player state
    const player = new PlayerState();
    player.sessionId = client.sessionId;
    this.state.players.set(client.sessionId, player);

    // Send welcome message
    client.send('welcome', { sessionId: client.sessionId });
  }

  onLeave(client: Client, consented: boolean) {
    console.log(`[Room ${this.roomId}] Client left: ${client.sessionId} (consented: ${consented})`);

    // Remove player from state
    this.state.players.delete(client.sessionId);
  }

  onDispose() {
    console.log(`[Room ${this.roomId}] Disposed`);
  }

  private gameLoop(deltaTime: number) {
    // Game logic here
  }
}

Room Configuration Best Practices

Configuration	Value	Purpose
maxClients	64	FFA mode capacity
patchRate	50ms	20Hz state sync for multiplayer
autoDispose	true	Cleanup when empty (default)
setSimulationInterval	16.6ms	60Hz game loop (optional)

Message Handler Pattern

// Specific message type
this.onMessage('move', (client, data) => {
  const player = this.state.players.get(client.sessionId);
  if (player) {
    player.x = data.x;
    player.y = data.y;
  }
});

// Catch-all for other messages
this.onMessage('*', (client, type, data) => {
  console.log(`Unhandled message: ${type}`, data);
});

Sources:

• https://docs.colyseus.io/colyseus/server/room/
• Learned from arch-003 retrospective (2026-01-28)