Programming Flash Communication Server

This is the Title of the Book, eMatter Edition

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

The Communication Classes

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wrong keyframe. If the client did, the video image would be made up of a mosaic of 8

x 8 pixel blocks from two different frames. RTMP also prioritizes data. Audio is

given the highest priority because it is so essential for real-time conversations. Video

is given the lowest priority, and ActionScript is given a priority in between audio and

video.

The Communication Classes

While RTMP conveniently manages the flow of multiple streams of data across a net-

work, the real power of Flash and FlashCom for developers is realized in the high-

level classes that make connecting to the server, sharing information, and streaming

audio and video so easy and flexible. I’ll briefly review the major classes, which will

be explored in more detail and used in examples throughout the remainder of the

book.

Connecting to the Server

The NetConnection class connects a client to an application instance on a server. In

the simplest case, you can create a connection by invoking NetConnection.connect( )

with the URI of the remote application:

nc = new NetConnection( );

nc.connect("rtmp://echo.ryerson.ca/campusCameras/connector");

To determine if the connection was established successfully, define an onStatus( )

method on the NetConnection object before invoking connect( ):

nc = new NetConnection( );

nc.onStatus = function (info) {

trace("The connection code is: " + info.code);

};

nc.connect("rtmp://echo.ryerson.ca/campusCameras/connector");

In this example, the RTMP address includes the host (echo.ryerson.ca), the applica-

tion name (campusCameras), and the instance name (

connector). If you’ve ever

developed network applications using other application programming interfaces,

you’ll likely agree that creating a network connection between Flash and FlashCom

is ridiculously easy. Chapter 3 goes into greater detail on the NetConnection class and

how to use NetConnection objects.

Streaming Audio, Video, and ActionScript Data

Once you establish a connection using a NetConnection object in the client, you can

use it to send or receive a stream containing audio and/or video. Suppose you know

that a recorded Flash video file named Ryerson_High_Speed.flv is available in the

instance’s public directory. You can attach the video stream to a video object, here

named

videoArea, using Video.attachVideo( ) and play it using NetStream.play( ). The