ActionScript 3.0 API supporting RTMFP

There is a new ActionScript 3.0 API in Flash Player 10 to support RTMFP. Connecting to the Stratus service and creating end-to-end media streams are analogous to working with Flash Media Server. Please note that you must use ActionScript 3.0 with either Flash Professional CS4 or Flex Builder 3 targeting Flash Player 10 or AIR 1.5.

As I mentioned before, first you must connect to the Adobe Stratus service:

private const StratusAddress:String = "rtmfp://stratus.adobe.com";
private const DeveloperKey:String = "your-developer-key";
private var netConnection:NetConnection;
 
netConnection = new NetConnection();
netConnection.addEventListener(NetStatusEvent.NET_STATUS,
netConnectionHandler);
netConnection.connect(StratusAddress + "/" + DeveloperKey);

The developer key is issued when you sign up for an Adobe Developer Connection account and is available on the Adobe Stratus beta service site.

Upon successful connection to Stratus, you get a NetConnection.Connect.Success event. There could be several reason for connection failure. If you provide an invalid developer key or incorrectly specify Stratus address, you'll receive NetConnection.Connect.Failed. If your firewall blocks outgoing UDP traffic, you'll receive the NetConnection.Connect.Failed event after a 90-second timeout.

After successfully establishing a connection to the Stratus service, you are assigned a unique 256-bit peer ID (NetConnection.nearID). Other Flash Player endpoints must know this peer ID in order to receive your published audio/video streams. It is out of the scope of Flash Player or the Stratus service how these peer IDs are exchanged among Flash Player endpoints. For exchanging peer IDs, you may use an XMPP service or a simple web service, as the Video Phone sample application does.

Direct communications between Flash Player instances is conducted using unidirectional NetStream channels. That is, if you want two-way voice conversation, each Flash Player endpoint must create a sending NetStream and a receiving NetStream.

First, create a sending NetStream:

private var sendStream:NetStream;
 
sendStream = new NetStream(netConnection, NetStream.DIRECT_CONNECTIONS);
sendStream.addEventListener(NetStatusEvent.NET_STATUS,
netStreamHandler);
sendStream.publish("media");
sendStream.attachAudio(Microphone.getMicrophone());
sendStream.attachCamera(Camera.getCamera());

This means that media is published as an end-to-end stream. Since Stratus cannot relay media, you can publish only end-to-end streams. This stream will include both audio and video from your local default devices chosen by the Settings Manager.

Note: Audio/video is not sent out until another Flash Player endpoint subscribes to your media stream.

Now, create the receiving NetStream:

private var recvStream:NetStream;
 
recvStream = new NetStream(netConnection, id_of_publishing_client);
recvStream.addEventListener(NetStatusEvent.NET_STATUS, netStreamHandler);
recvStream.play("media");

At this point, you hear audio and you can create a Video object to display video. In order to create the receiving NetStream, you must know the 256-bit peer ID of the publisher (id_of_publishing_client). In order to receive audio/video, you must know the name of the stream being published.

Advanced topics

The publisher has fine control over which endpoint can receive its published stream. When a subscriber attempts to receive a published stream, the onPeerConnect() method is invoked (default implementation simply returns true) on the published NetStream. The publisher could disallow certain Flash Player endpoints to receive its media:

var o:Object = new Object();
o.onPeerConnect = function(subscriberStream:NetStream):Boolean
{
   if (accept) 
   {
      return true; 
   }
   else
   {
      return false; 
   }
}
sendStream.client = o; 

On the publisher side, the NetStream.peerStreams property holds all the subscribing instances of the publishing NetStream. For example, using sendStream.send() will send the same data to all subscribers. You can use the following to send information to a specific subscriber:

sendStream.peerStreams[i].send()

The NetConnection.maxPeerConnections property specifies the number of peer streams that are allowed to connect to the publisher. The default value is set to 8 but, in practice, depending on your application, you must consider that most ISPs provide asymmetric Internet access. Figure 1 illustrates the direct communication among three instances of Flash Player. Each Flash Player endpoint sends and receives two streams, creating a fully connected mesh. Since Internet download capacity is generally much higher than upload capacity, you must be extra careful not to overload the end-user's uplink.

Figure 1. End-to-end connections using the Stratus service

The NetConnection.unconnectedPeerStreams property is an array of NetStreams that are not associated with a publishing NetStream yet. When a publishing stream matches a subscribing stream name, the subscribing NetStream is moved from this array to the publishing NetStream.peerStreams array.

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