initial version

.gitignore

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+sync.js
+node_modules

package.json

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+{
+  "dependencies": {
+    "websocket": "^1.0.24"
+  },
+  "devDependencies": {
+    "@types/node": "^7.0.5",
+    "@types/websocket": "0.0.33",
+    "ts-node": "^2.1.0",
+    "typescript": "^2.2.1"
+  }
+}

sync.ts

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+import {server as WebSocketServer, request, connection} from 'websocket';
+import {createServer} from 'http';
+
+interface Session {
+	name: string;
+	owner: connection;
+	clients: connection[];
+	tick: number;
+	playing: boolean;
+}
+
+const sessions: {[name: string]: Session} = {};
+
+interface JoinPacket {
+	type: 'join';
+	session: string;
+}
+
+interface CreatePacket {
+	type: 'create';
+	session: string;
+}
+
+interface TickPacket {
+	type: 'tick';
+	session: string;
+	tick: number;
+}
+
+interface PlayPacket {
+	type: 'play';
+	session: string;
+	play: boolean;
+}
+
+type Packet = JoinPacket | CreatePacket | TickPacket | PlayPacket;
+
+const server = createServer(function (request, response) {
+	response.writeHead(404);
+	response.end();
+});
+server.listen(8181, function () {
+	console.log((new Date()) + ' Server is listening on port 8080');
+});
+
+const wsServer = new WebSocketServer({
+	httpServer: server,
+	autoAcceptConnections: false
+});
+
+function originIsAllowed(origin) {
+	return true;
+}
+
+wsServer.on('request', function (request) {
+	if (!originIsAllowed(request.origin)) {
+		// Make sure we only accept requests from an allowed origin
+		request.reject();
+		console.log((new Date()) + ' Connection from origin ' + request.origin + ' rejected.');
+		return;
+	}
+
+	const connection = request.accept('demo-sync', request.origin);
+	connection.on('message', function (message) {
+		if (message.type === 'utf8') {
+			const data = <Packet>JSON.parse(message.utf8Data);
+			switch (data.type) {
+				case 'create':
+					sessions[data.session] = {
+						name: data.session,
+						owner: connection,
+						clients: [],
+						tick: 0,
+						playing: false
+					};
+					break;
+				case 'join' :
+					if (sessions[data.session]) {
+						sessions[data.session].clients.push(connection);
+						connection.sendUTF(JSON.stringify({
+							type: 'tick',
+							tick: sessions[data.session].tick
+						}));
+						connection.sendUTF(JSON.stringify({
+							type: 'play',
+							tick: sessions[data.session].playing
+						}));
+					}
+					break;
+				case 'tick':
+					if (sessions[data.session]) {
+						sessions[data.session].tick = data.tick;
+						for (const client of sessions[data.session].clients) {
+							client.sendUTF(JSON.stringify({
+								type: 'tick',
+								tick: data.tick
+							}));
+						}
+					}
+					break;
+				case 'play':
+					if (sessions[data.session]) {
+						sessions[data.session].playing = data.play;
+						for (const client of sessions[data.session].clients) {
+							client.sendUTF(JSON.stringify({
+								type: 'play',
+								play: data.play
+							}));
+						}
+					}
+			}
+		}
+	});
+	connection.on('close', function (reasonCode, description) {
+		for (const name in sessions) {
+			if (sessions.hasOwnProperty(name)) {
+				const session = sessions[name];
+				if (session) {
+					const index = session.clients.indexOf(connection);
+					if (index !== -1) {
+						session.clients.splice(index, 1);
+					}
+					if (session.owner === connection) {
+						sessions[session.name] = null;
+						break;
+					}
+				}
+			}
+		}
+	});
+});