websocket-implementation

SKILL.md

WebSocket Implementation

Table of Contents

Overview

When to Use

Quick Start

Reference Guides

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:

Guide
Contents

Node.js WebSocket Server (Socket.IO)
Node.js WebSocket Server (Socket.IO)

Browser WebSocket Client
Browser WebSocket Client

Python WebSocket Server (aiohttp)
Python WebSocket Server (aiohttp)

Message Types and Protocols
Message Types and Protocols

Scaling with Redis
Scaling with Redis

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

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