Programming Flash Communication Server

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

A Simple Publisher/Subscriber Example

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To create a NetStream object within a network connection, the NetConnection object

must already exist and a connection attempt to FlashCom must have already been

made by calling the connect( ) method. In Example 5-1, a new NetConnection object

is created and then the user must enter both his username and the name of the

remote user he wants to talk to. Then he must click the Connect button. When the

connection is established, the NetConnection.onStatus( ) handler is called and two

NetStream objects are created and initialized to send or receive data. The NetStream

object that is designed to receive data tries to subscribe to a stream immediately, but

the outgoing stream does not attempt to send anything until the user clicks the Send

Stream button.

Publishing a Live Stream

In order to publish a stream, a NetStream object has to be created. In Example 5-1,

the

out_ns object is created within a connection by passing it a NetConnection object.

The keyword

this, which represents the current NetConnection object, is passed in

this example because the NetStream object is created within the NetConnection.

onStatus( ) method:

out_ns = new NetStream(this);

This statement could also have been written using the nc variable defined in the last

line of Example 5-1:

out_ns = new NetStream(nc);

Once the NetStream object out_ns exists, audio and video data sources can be

attached to it:

out_ns.attachAudio(Microphone.get( ));

out_ns.attachVideo(Camera.get( ));

The Microphone and Camera classes are available only within Flash movies (not on

the server) and provide a number of static methods, such as get( ). In the example,

Microphone.get( ) returns the Microphone object last selected in the movie’s Player

Settings dialog box. Passing the Microphone object to the out_ns.attachAudio( )

method makes the sound data captured from the microphone available to the

out_ns

stream. The Camera.get( ) method returns a Camera object and works in the same

way. Attaching the Camera object to the stream using the NetStream.attachVideo( )

method makes compressed video data from the camera available to the stream.

Although it isn’t a best practice to pass the return value from the get( ) methods

directly to the attachAudio( ) and attachVideo( ) methods, we use this approach for

demonstration purposes. Chapter 6 considers other alternatives.

The Camera and Microphone classes provide other methods for managing video and

audio sources and events, and are described in detail in Chapter 6.

Before actually publishing the stream, it is a good idea to set up an onStatus( ) event

handler that will receive notifications when stream events occur. In Example 5-1, a