server.js

/**
 * @author pschroen / https://ufo.ai/
 *
 * Remix of https://glitch.com/edit/#!/multiuser-sketchpad
 */

import express from 'express';
import enableWs from 'express-ws';

const interval = 4000; // 4 second heartbeat

const app = express();
const expressWs = enableWs(app);
expressWs.getWss('/');

app.use(express.static('public'));

//

import { ObjectPool } from '@alienkitty/space.js/three';

import { numPointers } from './src/config/Config.js';

const mousePool = new ObjectPool();

for (let i = 0; i < numPointers; i++) {
	mousePool.put(i);
}

//

const clients = [];
const room = new Array(255);

function getRemoteAddress(request) {
	return (request.headers['x-forwarded-for'] || request.connection.remoteAddress).split(',')[0].trim();
}

function getRemoteAddresses() {
	return clients.map(ws => ws._remoteAddress);
}

function getUsers() {
	if (!clients.length) {
		return;
	}

	const length = clients.length;
	const byteLength = 1 + 10 + 4 + 2; // mouse + nickname + remoteAddress + latency
	const data = Buffer.allocUnsafe(1 + byteLength * length); // event + size * users
	data.writeUInt8(0, 0);

	let index = 1;

	for (let i = 0; i < length; i++) {
		const client = clients[i];

		data.writeUInt8(client._mouse === null ? numPointers : client._mouse, index);

		const buf = Buffer.from(client._nickname, 'utf8');

		for (let j = 0; j < 10; j++) {
			data.writeUInt8(buf[j], index + 1 + j);
		}

		data.writeUInt32BE(ip2long(client._remoteAddress), index + 11);
		data.writeUInt16BE(client._latency, index + 15);

		index += byteLength;
	}

	// console.log('USERS:', data);

	return data;
}

function add(ws, request) {
	clients.push(ws);

	for (let i = 0, l = room.length; i < l; i++) {
		if (room[i] === undefined) {
			const remoteAddresses = getRemoteAddresses();

			let count = 1;
			let remoteAddress = getRemoteAddress(request);

			while (remoteAddresses.includes(remoteAddress)) {
				count++;
				remoteAddress = `${getRemoteAddress(request)} (${count})`;
			}

			ws._id = i;
			ws._idle = Date.now();
			ws._mouse = request.query.observer !== undefined ? null : mousePool.get();
			ws._nickname = '';
			ws._remoteAddress = remoteAddress;
			ws._latency;

			room[i] = ws;

			console.log('REMOTE:', ws._remoteAddress, request.headers['user-agent']);

			return;
		}
	}
}

function remove(ws) {
	let index = clients.indexOf(ws);

	if (~index) {
		clients.splice(index, 1);
	}

	index = room.indexOf(ws);

	if (~index) {
		room[index] = undefined;
	}

	if (ws._mouse !== null) {
		mousePool.put(ws._mouse);
	}
}

function broadcast(ws, data) {
	for (let i = 0, l = clients.length; i < l; i++) {
		const client = clients[i];

		if (client !== ws && client.readyState === client.OPEN) {
			client.send(data);
		}
	}
}

function idle() {
	const idleTime = Date.now() - 1800000; // 30 * 60 * 1000

	for (let i = 0, l = clients.length; i < l; i++) {
		const client = clients[i];

		if (client._idle === 0) {
			client._idle = Date.now();
		} else if (client._idle < idleTime) {
			client.terminate();
			console.log('IDLE:', client._id);
		}
	}
}

function users(ws) {
	broadcast(ws, getUsers());
}

app.ws('/', (ws, request) => {
	add(ws, request);

	console.log('USERS:', clients.length);

	ws.on('close', () => {
		remove(ws);
		users(ws);

		console.log('USERS:', clients.length);
	});

	ws.on('message', data => {
		ws._idle = 0;

		switch (data.readUInt8(0)) {
			case 1:
				// console.log('HEARTBEAT:', data);
				ws._latency = Math.min(65535, Date.now() - Number(data.readBigUInt64BE(2))); // Clamp to 65535
				break;
			case 2: {
				if (ws._mouse !== null) {
					// console.log('NICKNAME:', data);
					ws._nickname = Buffer.from(data.subarray(2), 'utf-8').toString();
					users(ws);
				}
				break;
			}
			case 3: {
				if (ws._mouse !== null) {
					data.writeUInt8(ws._mouse, 1);

					// console.log('MOTION:', data);
					broadcast(ws, data);
				}
			}
		}

		// console.log('MESSAGE:', data);
	});

	const heartbeat = () => {
		if (ws.readyState === ws.OPEN) {
			const data = Buffer.allocUnsafe(10);
			data.writeUInt8(1, 0);
			data.writeUInt8(ws._mouse === null ? numPointers : ws._mouse, 1);
			data.writeBigUInt64BE(BigInt(Date.now()), 2);

			ws.send(data);

			setTimeout(heartbeat, interval);
		}
	};

	heartbeat();
	users();
});

setInterval(() => {
	idle();
	users();
}, interval);

//

const listener = app.listen(process.env.PORT, () => {
	console.log(`Listening on port ${listener.address().port}`);
});

// https://stackoverflow.com/questions/1908492/unsigned-integer-in-javascript/7414641#7414641
function ip2long(ip) {
	let ipl = 0;
	ip.split('.').forEach(octet => {
		ipl <<= 8;
		ipl += parseInt(octet, 10);
	});
	return ipl >>> 0;
}