Using Node.js, Cygwin and Web Sockets

If you have not heard of Node.js (or “Node” as Ryan Dahl calls it) [LINK] it is more fun than a barrel full of monkeys and faster than stink. Node.js is built around the Google V8 javascript engine and aims to solve the issues of concurrency and blocking IO which are prevalent in todays web servers. It also improves over traditional OS threading by using an event model to handle requests. This leads to the ability to handle many more concurrent requests but also handle them faster since less memory is allocated on the heap for each new call.

I spent some time last week looking at Web Sockets as a way to push information to the client. Web sockets need a custom server, not an HTTP server, so I used Nugget which is an open source implementation of the web socket protocol on CodePlex (http://nugget.codeplex.com/). Nugget worked great but with all the hype and interest around Node I felt I was missing something so I built the same thing again, this time around using Node.js on the server side.

Before get started you’ll need to build Node. This can be done

“on Linux, Macintosh, and Solaris. It also runs on Windows/Cygwin, FreeBSD, and OpenBSD. The build system requires Python 2.4 or better. V8, on which Node is built, supports only IA-32, x64, and ARM processors. V8 is included in the Node distribution. To use TLS, OpenSSL is required. There are no other dependencies.”

I used Cygwin on Wintel and installed g++, Python 2.7 and GNU Make. You also need OpenSSL if you plan on using Node with Web Sockets.

Here’s a comprehensive walkthrough of installing Cygwin and building Node from scratch: [LINK]

Web Sockets uses a funky little handshake protocol [LINK] to establish the connection which I didn’t feel like implementing so I came across a WS Server implementation using Node.JS up on GitHub [https://github.com/miksago/node-websocket-server/]. This worked well with Node 0.2.5 testing from Chrome 12 which uses v-76 of the Hixie protocol.

Here’s my client which is based off the Dive into HTML5 example:

if(Modernizr.websockets){
	    connect('ws://localhost:3400/service');
	} else {
		log ('web sockets not supported');
	}
	var ws;

	function connect(host) {
		ws = new WebSocket(host);
		ws.onopen = function () {
			log('connected');
		};

		ws.onmessage = function (evt) {
			log('recv :' + evt.data);
			showNotification(evt.data);
		};

		ws.onclose = function () {
			log('socket closed');
		};

		ws.onerror = function (evt) {
			log('<span style="color: red;">ERROR:</span> ' + evt.data);
		};
	};

	function log(msg){
		document.getElementById('log').innerHTML += msg + "<br/>";
	}

	function send(){
		var msg = document.getElementById('status').value;
		ws.send(msg);
	}

	function RequestPermission (callback) {
		window.webkitNotifications.requestPermission(callback);
	}

	function showNotification(msg){
		if (window.webkitNotifications.checkPermission() > 0) {
			RequestPermission(showNotification);
		}
		else {
			window.webkitNotifications.createNotification("alert.jpg", "Test Notification", msg).show();
		}
	}

With this client-side scripe and Node running the ws-socket server I was able to get a simple echo running forth between the web page and the server.

Node has gained some ground since I first looked at it (back when Chrome was on version 8). Even Microsoft has announced plans to port it over to Windows [LINK]. In the coming weeks I plan on looking at some of the templating engines (Like http://jade-lang.com/ and http://mustache.github.com/) and web frameworks (like http://expressjs.com and http://geddyjs.org/ ) which have cropped up around it and will report back on whether it’s ready for prime time or not. Watch this space.

Attribution: Today’s image by Casch52 on Flickr [LINK]