Programming Flash Communication Server

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Chapter 4: Applications, Instances, and Server-Side ActionScript

ActionScript 2.0. Again, see Essential ActionScript 2.0 for a full discussion of client-

side ActionScript classes and packages.

The Life of an Application Instance

An application instance is a process that runs in FlashCom. Each instance has:

• Its own script engine

• A namespace of streams and shared objects

• Persistent data that can be stored within its namespace

No two instances can share or update the same data directly, but they can play the

same stream in a virtual stream directory (see Chapter 5).

FlashCom maintains a pool of threads for script processing, and each application

uses one thread from this pool to execute server-side scripts in response to events

such as loading an instance or a Flash client connecting to an instance. Server-side

scripts should be designed to handle events quickly and then release the thread they

are using. When an error is thrown in one instance, it will not affect the other

instances.

FlashCom can run many different instances of the same application. Each instance is

usually created by FlashCom in response to a connection request from a client.

FlashCom receives the client’s connection request and examines the RTMP address

passed by the client to the server. The RTMP address forwarded by the client is the

URI passed into the client-side NetConnection.connect( ) method. As described in

Chapter 3, FlashCom extracts the application name and then runs an instance of the

application. If no instance name is provided in the RTMP address, it creates an

instance named

_definst_. Otherwise, it creates the instance named in the URI.

Depending on how the application is scripted and how the server is configured, some

time after the last client disconnects, the instance will be destroyed. Between the

time an instance is created and destroyed, a number of things can happen. To sim-

plify how things work, they are divided here into three sections: startup, midlife, and

shutdown.

Startup

An instance is normally started by FlashCom when the first client attempts to con-

nect to it. However, it may be started manually with the App Inspector or Adminis-

tration Console, or an application instance can be made to start immediately after

the server is started by setting the contents of the

<LoadOnStartup> tag in an Applica-

tion.xml file (see “Using load( ) to Include Other Script Files” later in this chapter for

details on where to place the Application.xml file).