synchroscope ($YNC)

synchroscope makes it very easy in to share AngularJS scope variables across multiple clients. It can be used to make a real-time interactive web application that runs on multiple devices.

Demo

• AngularJS Todos Demo
• Tic Tac Toe Game

Demo Server

A demo server for Synchroscope is available at http://synchroscope.herokuapp.com/, so you can experiment with Synchroscope.

Note that the server may restart (and the database reset) at any time!

Client

Symlink or copy client/sync.js to your Angular project, and include it along with socket.io.js.

If you include CryptoJS.MD5 on your page, synchroscope will generate revision IDs based on the cryptographic hash of the content instead of random string, which may help prevent editing conflicts a little bit.

<script src="/socket.io/socket.io.js"></script>
<script src="path/to/md5.js"></script><!-- recommended -->
<script src="path/to/sync.js"></script>

Then, declare a dependency on synchroscope module, ask for the $ync service, and just call it:

angular.module('myApp', ['synchroscope'])
  .controller('MyController', function($scope, $ync) {

    $scope.hello = 'initial data'
    $scope.world = 'for synchroscope demo'
    $scope.foo = 'TRY IT!'

    var keys = ['hello', 'world']  // keys that you want to share
    var room = 'test'              // room name
    var sync = $ync($scope, keys, room)
    
  })

As soon as you call $ync, the keys hello and world will be synchronized across all browser clients who are in the same server and same room.

When the initial synchronization is made, the $scope.$ynchronized property will become true. You can check that property to display loading screen or something.

Specifying the Room and Server

The third argument for the $ync function can be in form of:

• http://hostname:port/synchroscope#roomName
  • The server and path is specified before the hash sign.
• roomName
  • The server is assumed to be the same server, with path /synchroscope. This is the same as /synchroscope#roomName.

Server

Let's assume that io is a Socket.IO server object obtained by something like this: var io = require('socket.io').listen(server). Just add this line to your server:

require('synchroscope').listen(io.of('/synchroscope'))

Projects Using synchroscope

• Freshy Camp Registration Webapp. Synchroscope was made for this app. Actually, it was extracted from this app.
• shoutpraises. Web based remotely controlled worship lyrics presentation application.

Limitations

• All synchronized data must be JSON.stringifyable (with the exception of undefined, which is handled specially).
• This server stores all states in-memory. This server will not scale across multiple processes.
• Each variable synchronizes on its own. If a client sets 2 variable at the same time, it is possible that other clients may receive one variable before another.
• When the server is restarted, funny things may happen. (clients may go out of sync)
  • If you restart your web server often, then it may be a good idea to run a synchroscope server separately... as easy as node --eval 'require("synchroscope").listen(require("socket.io").listen(8008).of("/synchroscope"))'.

License

MIT.