drw/server.js

const { WebSocket, WebSocketServer } = require("ws");
const express = require("express");

const PORT = process.env.PORT || 3000;
const index = "index.html";

const server = express()
	.use(express.static("public"))
	.get("/", (req, res) => {
		res.sendFile("index.html", { root: __dirname });
	})
	.get("/destination", (req, res) => {
		res.sendFile("destination.html", { root: __dirname });
	})
	.listen(PORT, () => console.log(`Listening on ${PORT}`));

const wss = new WebSocketServer({ server, clientTracking: true });

let DESTINATIONS = new Set();
let USERS = new Set();
var theme = "";

const messageProcessor = {
	default: (ws, msg) => unknownMsg(msg),
	hello: (ws, msg) => registerDest(ws, msg),
	drawings: (ws, msg) => toDest(msg),
	theme: (ws, msg) => ((theme = msg.theme), broadcast(msg)),
};

const unknownMsg = (msg) => {
	console.log("Unknown message type...");
	console.log(msg);
};

const registerDest = (ws, msg) => {
	console.log("Destination client connected");
	DESTINATIONS.add(ws);
	ws.on("close", () => {
		DESTINATIONS.delete(ws);
	});
};

const toDest = (msg) => {
	DESTINATIONS.forEach((DESTINATION) => {
		if (DESTINATION?.readyState === WebSocket.OPEN) {
			DESTINATION.send(JSON.stringify(msg));
		}
	});
};

const broadcast = (msg) => {
	let message = JSON.stringify(msg);
	for (const user of USERS.values()) {
		if (user?.readyState === WebSocket.OPEN && !DESTINATIONS.has(user)) {
			user.send(message);
		}
	}
};

wss.on("connection", (ws) => {
	USERS.add(ws);
	ws.send(JSON.stringify({ type: "theme", theme: theme }));

	ws.on("message", (data) => {
		let message;
		try {
			message = JSON.parse(data);
		} catch (e) {}

		if (message) {
			(messageProcessor[message.type] || messageProcessor.default)(ws, message);
		}
	});

	ws.on("close", () => {
		USERS.delete(ws);
	});
});