WebSocket Additions

Home of the AwesomeWebSocket

What is this thing?

concise

WebSockets should do some stuff out of the box that they don't, this package attempts to add that stuff.

blowhard

It appears useful to add some basic functionality to the native WebSocket. At the very least, it appears as if people find themselves coding the same basic functionality around the native WebSocket as we convert applications to be more WebSocket centric. This package intends to be a source of some of that common functionality bundled up for re-use, to avoid having people need to do the same things over and over.

What is this functionality you're speaking of?

• Reconnecting - in the event of the server going down intentionally or otherwise it's good to have the socket just pickup as if the server were never gone.
• Hunting - given a list of hosts, connect to them and send messages to which ever one is available, switching to another if the 'active' connection becomes unavailable. Dumb-as-dirt client side fail over.
• KeepAlive - You've gotta have your server do some work for this one, but it will allow you to set up a message that will be periodically sent back to the server (to which the server should respond) to keep your connection up and healthy.
• Sending Objects - really, if you send an object you'd probably just like it to get JSON serialized... so... that's what these do.

You sure it works?

While the only place this currently has been tested is in Chrome and Safari (newish versions), there are some QUnit tests available to prove it does (or doesn't) work.

git clone https://github.com/igroff/ws-additions.git
cd ws-additions/
make watch

Once you've done that successfully you should find a test pages at

• http://localhost:8080/index.html
• http://localhost:8080/hunting.html
• http://localhost:8080/reconnecting.html
• http://localhost:8080/keepalive.html

A bunch of these tests blow up the server ( by design ) so it's hard to get them all to run at the same time ( hence the multiple pages ).

Usage!

This package makes an object that looks a fair bit like a WebSocket available to you.

What's a ReconnectingWebSocket look like?

[Constructor(DOMString url)]
interface ReconnectingWebSocket : EventTarget {
  attribute WebSocket underlyingWs;

  // networking
          attribute EventHandler onopen;
          attribute EventHandler onerror;
          attribute EventHandler onclose;
  // ondisconnect is a convenience that is intended for testing, but in the 
  // spirit of transparency...
          attribute EventHandler ondisconnect;
  void close([Clamp] optional unsigned short code, optional DOMString reason);

  // messaging
          attribute EventHandler onmessage;
  void send(DOMString data);
  void send(Blob data);
  void send(ArrayBuffer data);
  void send(ArrayBufferView data);

  void keepAlive(int timeoutMs, DOMString message)
  void keepAlive(int timeoutMs, Object message)

What's a AwesomeWebSocket look like?

[Constructor([DOMString url] | DOMString url)]
interface AwesomeWebSocket : EventTarget {
  attribute WebSocket currSocket;

  // networking
          attribute EventHandler onopen;
          attribute EventHandler onerror;
          attribute EventHandler onclose;
  void close();

  // messaging
          attribute EventHandler onmessage;
  void send(DOMString data);
  void send(Blob data);
  void send(ArrayBuffer data);
  void send(ArrayBufferView data);

  void keepAlive(int timeoutMs, DOMString message)
  void keepAlive(int timeoutMs, Object message)

First of all, you'll to get the sucker into a format usable by your browser. 'round here we like browserify.

npm install ws-additions
browserify -r ws-additions --outfile www/js/reconn.js

:shit: If you really want to, the most recent browserified version of this thing is down there in test/www/js/reconn.js

Then in an HTML page somewhere above js/reconn.js

You can, for whatever strange reason, use the ReconnectingWebSocket that underlies AwesomeWebSocket ( AwesomeWebSocket is way more awesome tho ).

<script src="js/reconn.js"></script>
<script>
  var ReconnectingWebSocket = require("ws-additions").ReconnectingWebSocket;
  var ws = new ReconnectingWebSocket("ws://localhost:8080/socket");
  // now ws will reconnect in the event that the server busts, the only problem
  // is that you may lose any messages not sent to the server
</script>

With that, your ws will handle reconnecting for you in the event that the server at ws://localhost:8080/socket disappears.

For awesome, the only real difference is that you need to provide a list of servers to connect to, if any of them choose to vanish... it'll handle that for you.

<script src="js/reconn.js"></script>
<script>
    var AwesomeWebSocket = require("ws-additions").AwesomeWebSocket;
    var testWs = new AwesomeWebSocket([
      "ws://localhost:8085/socket",
      "ws://localhost:8086/socket"
    ]);
    testWs.send("this message is AWESOME!");
    testWs.send({thisIs: "an object"}); // YAY!
</script>

But, maybe you only have one server or already do load balancing for your servers. In that case, just give it a single url as a string.

<script src="js/reconn.js"></script>
<script>
    var AwesomeWebSocket = require("ws-additions").AwesomeWebSocket;
    var testWs = new AwesomeWebSocket("ws://localhost:8085/socket");
    testWs.send("this message is AWESOME!");
    testWs.send({thisIs: "an object"}); // YAY!
</script>

Proxies have fun with Websockets. Nginx in particular has a great default that will kill the connection if it is idle for too long. So you can opt to have these websockets send pings to your server every so often. It works the same way for each of the aforementioned sockets, you call keepAlive passing an interval (in ms) and a message that your server will respond to.

<script src="js/reconn.js"></script>
<script>
  var AwesomeWebSocket = require("ws-additions").AwesomeWebSocket;
  var ws = new AwesomeWebSocket("ws://localhost:8080/socket")
  ws.onopen = function() {
    // this sets up the keep alive
    ws.keepAlive(60 * 1000, "ping!");
  }

</script>