2.1.1 • Public • Published


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


  • 🔌 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.


  • Node >= v8.0.0


npm add netcode

Get started

Define a list of events

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

// events.js
import Int8Codec from 'netcode/src/encoder/codec/Int8Codec';
import StringCodec from 'netcode/src/encoder/codec/StringCodec';

export default [
	['id', new Int8Codec()],
	['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 to this 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 an 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 from 'netcode/src/server/Server';
import BinaryEncoder from 'netcode/src/encoder/BinaryEncoder';
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));

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

See an 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 from 'netcode/src/client/Client';
import BinaryEncoder from 'netcode/src/encoder/BinaryEncoder';
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 client that listen for the id event and sent a sentence in a say event.

Connection is alive and well!

See an full example of client setup.

Complete documentation

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

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npm i netcode

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  • tom32i