WebSocket Implementation

Table of Contents

• [Overview](#overview)
• [When to Use](#when-to-use)
• [Quick Start](#quick-start)
• [Reference Guides](#reference-guides)
• [Best Practices](#best-practices)

Overview

Build scalable WebSocket systems for real-time communication with proper connection management, message routing, error handling, and horizontal scaling support.

When to Use

• Building real-time chat and messaging
• Implementing live notifications
• Creating collaborative editing tools
• Broadcasting live data updates
• Building real-time dashboards
• Streaming events to clients
• Live multiplayer games

Quick Start

Minimal working example:

const express = require("express");
const http = require("http");
const socketIo = require("socket.io");
const redis = require("redis");

const app = express();
const server = http.createServer(app);
const io = socketIo(server, {
  cors: { origin: "*" },
  transports: ["websocket", "polling"],
  reconnection: true,
  reconnectionDelay: 1000,
  reconnectionDelayMax: 5000,
  reconnectionAttempts: 5,
});

// Redis adapter for horizontal scaling
const redisClient = redis.createClient();
const { createAdapter } = require("@socket.io/redis-adapter");

io.adapter(createAdapter(redisClient, redisClient.duplicate()));

// Connection management
const connectedUsers = new Map();

// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Best Practices

✅ DO

• Implement proper authentication
• Handle reconnection gracefully
• Manage rooms/channels effectively
• Persist messages appropriately
• Monitor active connections
• Implement presence features
• Use Redis for scaling
• Add message acknowledgment
• Implement rate limiting
• Handle errors properly

❌ DON'T

• Send unencrypted sensitive data
• Keep unlimited message history in memory
• Allow arbitrary room/channel creation
• Forget to clean up disconnected connections
• Send large messages frequently
• Ignore network failures
• Store passwords in messages
• Skip authentication/authorization
• Create unbounded growth of connections
• Ignore scalability from day one