RTMP Data Push from .NET to Flex

        

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Timers;

using Weborb.Messaging.Api.Service;
using Weborb.Messaging.Api;
using Weborb.Messaging.Server.Adapter;

namespace CPUMonitor
{
  public class CPUMonitoringAppHandler : ApplicationAdapter
  {
    private Timer cpuReadingTimer;
    private PerformanceCounter cpuCounter;

    // invoked when WebORB for .NET starts up
    public override bool appStart( IScope app )
    {
      bool appStarted = base.appStart( app );

      // if application could not start for any reason, do not
proceed further
      if( !appStarted )
        return appStarted;

      // initialize performance counter
      cpuCounter = new PerformanceCounter();
      cpuCounter.CategoryName = "Processor";
      cpuCounter.CounterName = "% Processor Time";
      cpuCounter.InstanceName = "_Total";

      // start thread to get CPU readings
      cpuReadingTimer = new Timer( 1000 );
      cpuReadingTimer.Elapsed += new ElapsedEventHandler(
cpuReadingTimer_Elapsed );
      cpuReadingTimer.Start();
      return appStarted;
    }

    void cpuReadingTimer_Elapsed( object sender, ElapsedEventArgs
e)
    {
      // ignore timer event, if there are no connected clients to
the scope
      if( scope.getClients().Count == 0 )
        return;

      // get the CPU reading
      float cpuUtilization = cpuCounter.NextValue();

      // create an array of values to deliver to the client.
      // there is only one value, but the API requires it to be an
array
      object[] args = new object[] { cpuUtilization };

      // get an enumeration of connections to this application
      IEnumerator<IConnection> connections =
scope.getConnections();

      while( connections.MoveNext() )
      {
        IConnection connection = connections.Current;

        // invoke client-side function to deliver CPU reading
        if( connection is IServiceCapableConnection )
          ((IServiceCapableConnection) connection).invoke(
"processCPUReading", args );
      }
    }
  }
}
  

Registering Messaging Application

1. Locate the /Applications folder in the root of your WebORB installation. If you use WebORB version 3 for .NET, the folder is located in /inetpub/wwwroot/weborb30/. If you use WebORB version 4 for .NET, the folder is under /Program Files/WebORB/4.0/
2. Create CPUMonitoringApp subfolder under Applications/. The name of the folder is going to be the name of the application. This is the name Flex clients will use to connect to the server/application.
3. Download this file and extract its contents into the CPUMonitoringApp directory. Once you do that the directory should have app.config file inside. For the verification purposes, open app.config and make sure the name of the class in the application-handler element matches the full type name of your application handler.
4. You can use WebORB Management Console to verify if the messaging application is properly deployed. if you use WebORB version 3 select Management and then Messaging Server. The name of the application (CPUMonitoringApp) should appear in the list of application. With version 4 of WebORB, you should see the name of the application on the main overview screen.

Developing Flex Code

                        <?xml version="1.0"
encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
  xmlns:s="library://ns.adobe.com/flex/spark" 
  xmlns:mx="library://ns.adobe.com/flex/halo"
  creationComplete="init()">
<fx:Declarations>
</fx:Declarations>
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
import mx.controls.Alert;

[Bindable]
private var cpuValues:ArrayCollection = new ArrayCollection();
private var serverConnection:NetConnection;

private function init():void
{
  serverConnection = new NetConnection();
 
serverConnection.addEventListener(NetStatusEvent.NET_STATUS,handleStatus
);
  serverConnection.client = this;
  serverConnection.connect(
"rtmp://localhost:2037/CPUMonitoringApp");

  for( var i:int = 0; i < 100; i++ )
    cpuValues.addItem( 0 );
}

private function handleStatus( evt:NetStatusEvent ):void
{
  switch( evt.info.code )
  {
    case "NetConnection.Connect.Success":                
     break;
    case "NetConnection.Connect.Failed":
     Alert.show( "Unable to connect to WebORB", "Connection Error"
);
     break;                     
  }
}

public function processCPUReading( cpuUtilization:Number ):void
{
  // create sliding chart effect
  cpuValues.removeItemAt( 0 );
  cpuValues.addItem( cpuUtilization );
}
]]>
</fx:Script>
<s:Panel left="5" right="5" top="5" bottom="5" 
           title="Server CPU Utilization">
<mx:LineChart id="cpuChart" 
                  left="10" right="10" top="10" bottom="10"
       dataProvider="{cpuValues}">
<mx:series>
<mx:LineSeries displayName="CPU(%)" yField=""/>
</mx:series>
</mx:LineChart>
</s:Panel>
</s:Application>
     
     
     
      

The client code uses the NetConnection API to connect to the server and receive server-to-client (DataPush) callbacks. The "serverConnection" variable is declared on line 16 and initialized on lines 20-26. Notice the URL of the messaging application on line 26. The "CPUMonitoringApp" part of the URL refers to the messaging application created earlier in the article. It is also important to note the assignment on line 24. The "client" property on NetConnection refers to the object which contains the methods invoked from the server-side. In this example, the same object (the Flex application itself) hosts the method invoked on the server. The method is "processCPUReading" (lines 45-50). The method receives an argument value delivered by the server. The value is stored in a bindable ArrayCollection - variable "cpuValues". The chart (lines 55-61) uses cpuValues as the data provider. As soon as the code updates the values in the array collection, the chart is automatically updated. 

 

Download full MXML listing of the example.

Running the Example

When you run the example, you should immediately see data in the chart. You can try running multiple browsers with the example application. If the data does not arrive, make sure the WebORB messaging server is running - you can do that by opening the WebORB Management Console.

A copy of this recipe is also available on the Midnight Coders site at:

http://www.themidnightcoders.com/products/weborb-for-net/developer-den/technical-articles/rtmp-data-push-from-net-to-flex.html