Introduction

Goal of the tutorial

This tutorial aims to guide you in building real-time multiplayer games. We'll cover important aspects like real-time client-server communication, game state synchronization, and more.

What you'll learn

By the end of this tutorial, you'll be able to:
- Understand the client-server model for real-time games
- Implement game state synchronization
- Build a basic real-time multiplayer game

Prerequisites

Basic knowledge of JavaScript and Node.js is required. Familiarity with WebSockets would be beneficial.

Step-by-Step Guide

1. Understanding Client-Server Model

In a real-time multiplayer game, multiple clients (players) interact with the server. The server maintains the game's state and sends updates to all clients. WebSockets is a communication protocol allowing real-time, bi-directional, communication between client and server.

2. Implementing Game State Synchronization

To keep all players in sync, the server continuously broadcasts the game state to all clients. When a client performs an action, it sends a message to the server, which updates the game state and broadcasts it.

3. Building the Game

We'll build a simple multiplayer game where players move around a board. The server will manage the players' positions and broadcast them.

Code Examples

1. Setting up the Server

// Require the necessary modules
const http = require('http');
const WebSocket = require('ws');

// Create an HTTP server
const server = http.createServer();

// Create a WebSocket server
const wss = new WebSocket.Server({ server });

// Array to store player positions
let players = [];

wss.on('connection', ws => {
  ws.on('message', message => {
    // Update player position based on received message
    // Then broadcast the new player positions
  });
});

// Start the server on port 8080
server.listen(8080);

This sets up the server and WebSocket connection. When a message (player action) is received, it's processed, the game state is updated and then broadcasted.

2. Client Side

// Create a WebSocket connection to the server
const ws = new WebSocket('ws://localhost:8080');

ws.onopen = () => {
  console.log('Connected to server');
};

ws.onmessage = message => {
  // Update game state based on received message
};

// Send player action to the server
ws.send('player action');

This connects the client to the server and listens for messages (game state updates). It also sends a player action to the server.

Summary

You've learned about the client-server model for real-time games, implemented game state synchronization, and built a simple multiplayer game. Next, you could learn about adding more features like player scoring, different player actions, etc. You can check out the Mozilla Developer Network for more resources.

Practice Exercises

1. Add player scoring to the game.
2. Implement different player actions.
3. Make the game support multiple simultaneous games.

Solutions

1. Add a score property to each player in the players array on the server. When a player scores, update their score and broadcast the new game state.
2. Add different types of messages that the client can send to the server, each representing a different action. Update the server to handle these new message types.
3. Instead of a single players array, have an array of games, each with its own array of players. When a message is received, find the game that the player is in, update it, and broadcast its new state to its players.