Tag Archives: flex

Static initializers in AS3

Recently, several people have asked whether it’s possible to create some kind of constructor for static classes in ActionScript 3, and the answer is: yes!

The solution is  a static initializer. This is a block of code, surrounded by curly brackets but no function or var declaration, that runs the first time a property or method of a static class is called. Static initializers are called before any property value is returned or function executed, in the same way a constructor always runs before you can access the properties or methods or a regular class.

    public class MyStaticClass
        // This is the static initializer
            trace("Running static initilizer!");
        // We're calling a secondary method so we can use local variables
        static private function staticInitializer():void
            var now:Date = new Date;
            baseColor = now.hours > 16 ? 0x000066 : 0x0000FF;

        static public var baseColor:uint;

Although it’s not strictly necessary to call a secondary method, Flash Player will throw an error if you declare local variables within the static initializer itself.

To prove that the static initializer is running first, simple trace out the baseColor property:


If it’s after 4pm, this will result in the following output in the console window:

Running the static initializer!

Too good for 2.5… Mesmotronic Multiuser Server 3 is coming!

Mesmotronic Multiuser Server 2
Mesmotronic Multiuser Server 2.5 was supposed to be a stepping stone to 3, but as development progressed it became clear that all the cool new stuff being added would go far beyond a simple point-release.

So, we’ve taken the decision to cancel 2.5 and continue development towards a new multi-platform release: Mesmotronic Multiuser Server 3.

More information coming soon…

Get ready for Mesmotronic Multiuser Server 2.5

Mesmotronic Multiuser Server 2
The next major release of Mesmotronic’s real-time server solution has entered the final stages of development and has been handed to our crack team of testers to put it through its paces.

Mesmotronic Multiuser Server 2.5 makes it even easier to add push data and real-time interactivity to you Flash, Flex and AIR applications by enabling ActionScript developers to build client and server functionality using nothing more than their existing knowledge and an easy-to-use ActionScript 3 API.

Watch this space for further announcements.

Essential Eclipse plug-ins for Flash Builder 4 and Burrito

With the recent relase of Adobe Flash Builder 4, we thought we’d flag up the update URLs for a few of our favourite Eclipse plug-ins to save you having to hunt around for them.

To install plug-ins:

  1. Copy the appropriate URL to your clipboard
  2. In Flash Builder, select Install New Software… from the Help menu
  3. Click Add, paste URL in the Location field and click OK
  4. Select the plug-ins to install and click Finish

If you’ve spotted anything we’ve missed, add a comment or  tweet it to @mesmotronic.


This URL contains links to most of the plug-ins hosted on Eclipse.org, allowing you to add functionality like ANT, JDT (Java Development Tools) and PDT (PHP Development Tools). You’ll also need to add this URL to Flash Builder to enable you to install other plug-ins, like soapUI:


Subclipse (SVN)

If you’re a regular user of version control, and you should be, the subclipse plug-in is essential:



For anyone who uses Web Services, soapUI offers a great way to view and test your services:


Android SDK

Now that you can develop application using AIR for Android, it could be argued that ADT (Android Developer Tools) isn’t necessarily essential, but if you’re looking to develop mobile apps for anything other than the latest handsets it’s definitely worth a look:



For anyone who makes regular use of the Tasks panel in FlashDevelop or Eclipse’s Java profile, this is a must.

You can download the plug-in here (requires manual installation).


Creating a simple HTTP proxy using PHP

Cross domain policy files, or rather a lack of them, are the bane of Flash and Flex developers’ lives. Whether it’s the Twitter API, data from Yahoo! Finance or one of any number of other data sources, the moment your SWF makes it to the web you’re faced with the same problem: Security Error!

The solution is to create a simple proxy on your server that can load the data for you and pass it to your application. If you’re using PHP, then this is about as simple as it gets:

// Too simple! (see comment below)
$url = $_REQUEST['url'];
if (preg_match('/\b(https?|ftp):\/\/*/', $url) !== 1) die;
echo (file_get_contents($url));

The preg_match ensures that the requested URL is valid and offers basic protection against anyone trying to maliciously access files on your server.

That’s it. Just paste that into a text file, save it as proxy.php and upload it to your server. You can then access any data you like simply by passing it a URL. Best of all, it works with both GET and POST, for example:


Happy proxy-ing!

Introduction to server-side applications for Mesmotronic Multiuser Server

Mesmotronic Multiuser Server 2
Server-side applications can add vital functionality to multiuser applications and games created using Mesmotronic Multiuser Server 2, including the ability to load and save files, communicate between rooms and applications, and push data to clients.

A server-side application is a standard ActionScript 3 SWF like any other, except that it cannot display any graphics and extends the MultiuserServerApplication class, rather than Sprite or MovieClip. Applications can therefore be created using any ActionScript 3 IDE, including Flex/Flash Builder, Flash CS3/4 and FlashDevelop.

In this tutorial, we’re going to create a very simple server-side application which sends, on request, a random colour to the client which the client will then apply to the stage. As usual, we’re assuming you have a reasonable working knowledge of ActionScript 3 and have Mesmotronic Multiuser Server installed locally, with the API added to your library path.

The first step in creating any new server-side application is to create a new document class which extends MultiuserServerApplication. Your initial class structure would typically look something like this:

    import com.multiuserserver.server.MultiuserServerApplication;

    public class RandomColourApp extends MultiuserServerApplication
        override public function main():void
            // Entry point

The main entry point is called immediately after the application property of your class (inherited from MultiuserServerApplication) has been initialized, enabling you to communicate with the outside world, and should be used in preference to a class constructor. Although we won’t be doing anything here in this tutorial, this is where you would normally configure your application and add any event listeners you may require.

By default, all calls made to the server by clients, via the MultiuserServerClient call method, will invoke public functions of your application class. So, to allow clients to request a random colour, we need to add a function called getColour:

    import com.multiuserserver.server.MultiuserServerApplication;

    public class RandomColourApp extends MultiuserServerApplication
        override public function main():void
            // Entry point

        public function getColour():uint
            return Math.round(Math.random()*0xFFFFFF);

Now that the function is in place, you simply need to publish your class in the usual way and copy the resulting SWF, RandomColourApp.swf, to a folder of the same name within the applications directory of Mesmotronic Multiuser Server. Based on the default installation folder, this would be:

 C:\Program Files\Mesmotronic\Mesmotronic Multiuser Server\applications\RandomColourApp\

Once copied, your application is ready to go.

Now, all we need to do is create a simple client application to test that our server-side application works (the elements which relate to the server call are highlighted):

    import com.multiuserserver.events.MultiuserServerEvent;
    import flash.events.IOErrorEvent;
    import flash.events.MouseEvent;

    public class RandomColourClient extends Sprite
        public var client:MultiuserServerClient;

        public function RandomColourClient()
            client = new MultiuserServerClient();
            client.addEventListener(MultiuserServerEvent.CONNECT, onConnect);
            client.addEventListener(IOErrorEvent.IO_ERROR, onIOError);
            client.delegate = this;
            client.connect("localhost", 2040, "RandomColourApp", 10);

            stage.addEventListener(MouseEvent.CLICK, onClick);

        public function onConnect(event:MultiuserServerEvent):void

        public function onIOError(event:Event):void
            trace("Connection Error.");

        public function onClick(event:MouseEvent):void
            client.call("getColour", null, "setColour");

        public function setColour(colour:uint):void
            graphics.drawRect(0, 0, stage.stageWidth, stage.stageHeight);

Publish the class above and you will find that every time you click on the stage it will change to the colour received from the server!

Obviously, this is just scratching the surface of what’s possible with server-side applications, but it should give you a good idea of how basic client-server interaction can be implemented.

We’ll be taking a look at more advanced functionality at a later date, but if you’d like to find out more in the mean time, there are several examples included with your Mesmotronic Multiuser Server installation (follow the link on your start menu), which are also available as a separate download.

Flex data binding with Mesmotronic Multiuser Server

Mesmotronic Multiuser Server 2
If you’re creating client applications for Mesmotronic Multiuser Server 2 in Flex 3 or 4, it’s worth noting that almost all of the properties of both the MultiuserServerClient and MultiuserServerClientInfo classes are bindable.

Why is this useful? It means you can create things like connection status indicators or display the client and room ID without having to add any additional event handlers to your code.

For example, if you have a button that should only be available to users when they’re connected to the server, you can simply bind the enabled property of the button to the connected property of an instance of MultiuserServerClient, in this case client:

<mx:Button label="Enabled when connected" enabled="{client.connected}" />

Or, alternatively:

<mx:Binding source="client.connected" destination="myButton.enabled" />

This is equally true of all MultiuserServerClientInfo class properties, which is accessed via the info property of any MultiuserServerClient instance:

<mx:Label text="{client.connected ? 'You are in room '+client.info.room : 'You are not connected'}" />

If you’re new to Flex data binding, Adobe has a quick start guide here.

Getting started with Mesmotronic Multiuser Server using Flex

Mesmotronic Multiuser Server 2
In this tutorial, we’ll be creating a simple peer-to-peer chat application using Mesmotronic Multiuser Server 2 and Flex 3 MXML.

We’re assuming that you already have at least a basic knowledge of MXML and ActionScript 3, that Mesmotronic Multiuser Server is installed locally and you have made the ActionScript API available to your chosen IDE. If you don’t already have an MXML editor, you can follow this tutorial using either FlashDevelop or the trial version of Flex Builder.

Regardless of which editor you’re using, the first step is to create a new Flex Project and open the main MXML file (usually called main.mxml, or similar).

First, create the various MXML elements of the application, starting by adding a new namespace declaration to the Application tag to allow you to instantiate classes from the Mesmotronic Multiuser Server API using MXML:

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

Next, add a new MXML tag to instantiate the MultiuserServerClient class, setup the event listeners and assign a delegate:


The delegate property indicates the class or object that contains functions you would like to make available to other clients and/or the server, in this case we’re making all of the public functions of the current class available.

The connect event is dispatched when you initially connect to the server, clientConnect when a new client joins the room (including you), clientDisconnect when a client leaves the room and ioError when a connection error occurs.

Next, create a Panel with a very simple form inside of it, made up of a large TextArea to display messages, a TextInput field to input messages and a button you can press to send messages which calls a function called showMessage on all of the clients in the current room using the run method of the MultiuserServerClient class:

<mx:Panel id="panel" title="Mesmotronic Multiuser Server Example" status="Connecting...">
  <mx:Form width="100%" defaultButton="{input_btn}">
    <mx:TextArea id="output_txt" width="400" height="160" editable="false" />
    <mx:TextInput id="input_txt" width="400" />
    <mx:Button id="input_btn" width="100" label="Send"
      click="client.run('showMessage', [client.info.clientIndex, input_txt.text]); input_txt.text = '';" />

The final MXML element is a creationComplete event in the Application tag. This will allow you to connect automatically once your Flex application has finished loading:

  creationComplete="client.connect('localhost', 2040, 'FlexExample', 10);"

Finally, we need to create the ActionScript functions necessary to handle the various MultiuserServerClient events:

    import com.multiuserserver.events.MultiuserServerEvent;
    import flash.events.IOErrorEvent;

    public function onConnect(event:MultiuserServerEvent):void
      panel.status = "Connected";
      output_txt.text += "Hi user "+client.info.clientIndex+", welcome to room "+client.info.room+"!\n";

    public function onClientConnect(event:MultiuserServerEvent):void
      if (event.clientIndex != client.info.clientIndex)
        output_txt.text += "User "+event.clientIndex+" has joined the room.\n";

    public function onClientDisconnect(event:MultiuserServerEvent):void
      output_txt.text += "User "+event.clientIndex+" has left the room.\n";

    public function onIOError(event:IOErrorEvent):void
      panel.status = "Unable to contact server";
      output_txt.text = "It was not possible to connect to the server, please ensure that Mesmotronic Multiuser Server 2 is running.";

    public function showMessage(clientIndex:int, text:String):void
      output_txt.text += "[User "+clientIndex+"] "+text+"\n";
      output_txt.verticalScrollPosition = output_txt.maxVerticalScrollPosition;

As you can see, there’s nothing complicated involved: the ActionScript functions simply populate the TextArea and update the Panel’s status. If you prefer, much of this functionality can be included within your MXML declarations.

And that’s it. Now all you need to do is run your application and send yourself a few messages to try it out!

For more information about the events, properties and methods of the MultiuserServerClient class, take a look at the API reference or browse through the examples included with your Mesmotronic Multiuser Server installation, a link to which can be found on your Start Menu.