Planning an approach to multiplayer game development - plays one of the most important roles in the further development of the whole project, because it includes a lot of criteria that we should take into account when creating a really high-quality product. In today's manifesto tutorial, we will look at an example of an approach that allows us to create really fast games, while respecting all security and anti-chit rules.
So, let's define the main criteria for us:
First, you need to set up a server on Node.js. The server will be responsible for all critical calculations and transferring updated data to the players.
Installing the environment
To create a server on Node.js, install the necessary dependencies:
mkdir multiplayer-game-server cd multiplayer-game-server npm init -y npm install socket.io
Socket.io makes it easy to implement real-time two-way communication between clients and server using web sockets.
Basic server implementation
Let's create a simple server that will handle client connections, retrieve data, calculate critical states and synchronize them between all clients.
// Create a simple socket IO server
const io = require('socket.io')(3000, {
cors: {
origin: '*'
}
});
// Simple example of game states
let gameState = {};
let playerSpeedConfig = {
maxX: 1,
maxY: 1,
maxZ: 1
};
// Work with new connection
io.on('connection', (socket) => {
console.log('Player connected:', socket.id);
// Initialize player state for socket ID
gameState[socket.id] = { x: 0, y: 0, z: 0 };
// work with simple player command for movement
socket.on('playerMove', (data) => {
const { id, dx, dy, dz } = parsePlayerMove(data);
// Check Maximal Values
if(dx > playerSpeedConfig.maxX) dx = playerSpeedConfig.maxX;
if(dy > playerSpeedConfig.maxY) dx = playerSpeedConfig.maxY;
if(dz > playerSpeedConfig.maxZ) dx = playerSpeedConfig.maxZ;
// update game state for current player
gameState[id].x += dx;
gameState[id].y += dy;
gameState[id].z += dz;
// Send new state for all clients
const updatedData = serializeGameState(gameState);
io.emit('gameStateUpdate', updatedData);
});
// Work with unsafe data
socket.on('dataupdate', (data) => {
const { id, unsafe } = parsePlayerUnsafe(data);
// update game state for current player
gameState[id].unsafeValue += unsafe;
// Send new state for all clients
const updatedData = serializeGameState(gameState);
io.emit('gameStateUpdate', updatedData);
});
// Work with player disconnection
socket.on('disconnect', () => {
console.log('Player disconnected:', socket.id);
delete gameState[socket.id];
});
});
// Simple Parse our binary data
function parsePlayerMove(buffer) {
const id = buffer.toString('utf8', 0, 16); // Player ID (16 bit)
const dx = buffer.readFloatLE(16); // Delta X
const dy = buffer.readFloatLE(20); // Delta Y
const dz = buffer.readFloatLE(24); // Delta Z
return { id, dx, dy, dz };
}
// Simple Parse of unsafe data
function parsePlayerUnsafe(buffer) {
const id = buffer.toString('utf8', 0, 16); // Player ID (16 bit)
const unsafe = buffer.readFloatLE(16); // Unsafe float
return { id, unsafe };
}
// Simple game state serialization for binary protocol
function serializeGameState(gameState) {
const buffers = [];
for (const [id, data] of Object.entries(gameState)) {
// Player ID
const idBuffer = Buffer.from(id, 'utf8');
// Position (critical) Buffer
const posBuffer = Buffer.alloc(12);
posBuffer.writeFloatLE(data.x, 0);
posBuffer.writeFloatLE(data.y, 4);
posBuffer.writeFloatLE(data.z, 8);
// Unsafe Data Buffer
const unsafeBuffer = Buffer.alloc(4);
unsafeBuffer.writeFloatLE(data.unsafeValue, 0);
// Join all buffers
buffers.push(Buffer.concat([idBuffer, posBuffer, unsafeBuffer]));
}
return Buffer.concat(buffers);
}
This server does the following:
Key points:
Now let's create a client part on Unity that will interact with the server.
To connect Unity to a server on Socket.IO, you need to connect a library that was designed for Unity.
In this case we are not bound to any particular implementation (in fact they are all similar), but just use an abstract example.
Using reactive fields for synchronization
We will use reactive fields to update player positions. This will allow us to update states without having to check the data in each frame via the Update() method. Reactive fields automatically update the visual representation of objects in the game when the state of the data changes.
To get a reactive properties functional you can use UniRx.
Client code on Unity
Let's create a script that will connect to the server, send data and receive updates via reactive fields.
using UnityEngine;
using SocketIOClient;
using UniRx;
using System;
using System.Text;
// Basic Game Client Implementation
public class GameClient : MonoBehaviour
{
// SocketIO Based Client
private SocketIO client;
// Our Player Reactive Position
public ReactiveProperty<Vector3> playerPosition = new ReactiveProperty<Vector3>(Vector3.zero);
// Client Initialization
private void Start()
{
// Connect to our server
client = new SocketIO("http://localhost:3000");
// Add Client Events
client.OnConnected += OnConnected; // On Connected
client.On("gameStateUpdate", OnGameStateUpdate); // On Game State Changed
// Connect to Socket Async
client.ConnectAsync();
// Subscribe to our player position changed
playerPosition.Subscribe(newPosition => {
// Here you can interpolate your position instead
// to get smooth movement at large ping
transform.position = newPosition;
});
// Add Movement Commands
Observable.EveryUpdate().Where(_ => Input.GetKey(KeyCode.W)).Subscribe(_ => ProcessInput(true));
Observable.EveryUpdate().Where(_ => Input.GetKey(KeyCode.S)).Subscribe(_ => ProcessInput(false));
}
// On Player Connected
private async void OnConnected(object sender, EventArgs e)
{
Debug.Log("Connected to server!");
}
// On Game State Update
private void OnGameStateUpdate(SocketIOResponse response)
{
// Get our binary data
byte[] data = response.GetValue<byte[]>();
// Work with binary data
int offset = 0;
while (offset < data.Length)
{
// Get Player ID
string playerId = Encoding.UTF8.GetString(data, offset, 16);
offset += 16;
// Get Player Position
float x = BitConverter.ToSingle(data, offset);
float y = BitConverter.ToSingle(data, offset + 4);
float z = BitConverter.ToSingle(data, offset + 8);
offset += 12;
// Get Player unsafe variable
float unsafeVariable = BitConverter.ToSingle(data, offset);
// Check if it's our player position
if (playerId == client.Id)
playerPosition.Value = new Vector3(x, y, z);
else
UpdateOtherPlayerPosition(playerId, new Vector3(x, y, z), unsafeVariable);
}
}
// Process player input
private void ProcessInput(bool isForward){
if (isForward)
SendMoveData(new Vector3(0, 0, 1)); // Move Forward
else
SendMoveData(new Vector3(0, 0, -1)); // Move Backward
}
// Send Movement Data
private async void SendMoveData(Vector3 delta)
{
byte[] data = new byte[28];
Encoding.UTF8.GetBytes(client.Id).CopyTo(data, 0);
BitConverter.GetBytes(delta.x).CopyTo(data, 16);
BitConverter.GetBytes(delta.y).CopyTo(data, 20);
BitConverter.GetBytes(delta.z).CopyTo(data, 24);
await client.EmitAsync("playerMove", data);
}
// Send any unsafe data
private async void SendUnsafeData(float unsafeData){
byte[] data = new byte[20];
Encoding.UTF8.GetBytes(client.Id).CopyTo(data, 0);
BitConverter.GetBytes(unsafeData).CopyTo(data, 16);
await client.EmitAsync("dataUpdate", data);
}
// Update Other players position
private void UpdateOtherPlayerPosition(string playerId, Vector3 newPosition, float unsafeVariable)
{
// Here we can update other player positions and variables
}
// On Client Object Destroyed
private void OnDestroy()
{
client.DisconnectAsync();
}
}
To ensure smooth gameplay and minimize latency during synchronization, it is recommended:
In order to simplify your work with a binary protocol - create a basic principle of data processing, as well as schemes of interaction with it.
For our example, we can take a basic protocol where:
1) The first 4 bits are the maxa of the request the user is making (e.g. 0 - move player, 1 - shoot, etc.);
2) The next 16 bits are the ID of our client.
3) Next we fill in the data that is passed through the loop (some Net Variables), where we store the ID of the variable, the size of the offset in bytes to the beginning of the next variable, the type of the variable and its value.
For the convenience of version and data control - we can create a client-server communication schema in a convenient format (JSON / XML) and download it once from the server to further parse our binary data according to this schema for the required version of our API.
It doesn't make sense to process every data on the server, some of them are easier to modify on the client side and just send to other clients.
To make you a bit more secure in this scheme - you can use client-side anti-chit system to prevent memory hacks - for example, my GameShield - a free open source solution.
We took a simple example of developing a multiplayer game on Unity with a Node.js server, where all critical data is handled on the server to ensure the integrity of the game. Using a binary protocol to transfer data helps optimize traffic, and reactive programming in Unity makes it easy to synchronize client state without having to use the Update() method.
This approach not only improves game performance, but also increases protection against cheating by ensuring that all key calculations are performed on the server rather than the client.
And of course, as always thank you for reading the article. If you still have any questions or need help in organizing your architecture for multiplayer project - I invite you to my Discord
You can also help me out a lot in my plight and support the release of new articles and free for everyone libraries and assets for developers:
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