Netcode

A simple JavaScript client & server binary-encoded websocket communication system aimed towards web video games development.

Features:

• 🔌 Server / Client duo, for node and the browser, that handle Websocket connection and communication.
• ⚡️ Handle the binary encoding and decoding of your data, with performances in mind.
• 📢 Listen for event dispatched over websocket with simple on/off event emitter system.
• 💬 Fallback to JSON for easy debugging.
• 🐹 Golang server port available, wire-compatible with the JavaScript client.

Requirements

• Node >= v24.0.0

Installation

npm add netcode

Get started

Define a list of events

The server and the client must share the same ordered list of events. An event is defined by its unique name and the corresponding codec, responsible for encoding and decoding the data.

// events.js
import { UInt8Codec, StringCodec } from 'netcode/encoder';

export default [
	['id', new UInt8Codec()],
	['say', new StringCodec()],
];

In this example, the event list define how to send the following events over websocket:

• client.send('id', 255);
• client.send('say', 'Hello world!');

Then you'll be able to listen for these events on the client as follow:

• client.on('id', id => { /* Do something */ });
• client.on('say', sentence => { /* Do something */ });

Now let's create a server and a client that use this event list.

Setup a Server

We setup a server specifying the port and host on which the server will listen and the type of encoder to use. Here we use a BinaryEncoder to communicate in binary over websocket, with the previously configured event list.

import { Server, BinaryEncoder } from 'netcode/server';
import events from './events';

// Listen on localhost:8080
const server = new Server(8080, 'localhost', new BinaryEncoder(events));

server.on('client:join', client => {
	client.on('say', sentence => console.log(sentence));
	client.send('id', client.id);
});

Now we've got a server running at localhost:8080 that listens for a say text event and sends an id integer event to every client that connects.

See a full example of server setup.

Write a Client

Now we write a client, for the browser, that connects to our running server on ws://localhost:8080 and use a BinaryEncoder with the same event list as the server.

import { Client, BinaryEncoder } from 'netcode/client';
import events from './events';

const client = new Client('ws://localhost:8080', new BinaryEncoder(events))

client.on('open', () => {
	client.on('id', id => console.log(`My id is ${id}.`));
	client.send('say', 'Hello world!');
});

Now we've got a client that listens for the id event and sends a sentence in a say event.

Connection is alive and well!

See a full example of client setup.

Complete documentation

To go further, see in-depth documentation and how-to's.

• Full API reference.
• Default codecs and how to write your own.
• About packaging and setting up your own bundler configuration.
• Use netcode over a custom domain name and/or secured SSL connection.
• Run a Netcode server in Go.