Programming Flash Communication Server

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A More Realistic Example

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The Client class cannot be subclassed because the Client constructor is never called

directly in a script. Whenever it is necessary to significantly extend the Client class,

you should use composition. Adding the

user object to each client and then delegat-

ing work, such as getting the client’s connection information, to the

user object is

one example of composition. Other objects can also be added in order to take on

other responsibilities on behalf of the client. For detailed discussions on attaching

methods to a class’s prototype, see ActionScript for Flash MX: The Definitive Guide.

For thorough discussions of composition versus inheritance, see Essential Action-

Script 2.0.

Limiting the Number of Client Connections

The number of currently accepted client connections is always available via the

length property of the application.clients array. Restricting the number of clients

that can connect at any one time is a simple matter of checking the

length property

and rejecting clients when it reaches a certain size. In some applications, it may be

necessary to allow unlimited connections from users of one type and restrict connec-

tions of another type. In Example 4-3, guest connections are not accepted when the

number of accepted clients reaches a certain point:

if (application.clients.length >= MAXCONNECTIONS && user.role == "guest") {

application.rejectConnection(client, {msg: "Chat is already full."});

return;

}

This example shows how to reject a connection to prevent it from being established.

You can use application.disconnect( ) at any time to disconnect a client that has

already been accepted.

Performing Periodic Updates with setInterval( )

You’ll often want to perform some action periodically. On the client side, this may

be achieved in several ways, such as using timelines or enterFrame events. However,

neither of these is available on the server. In server-side code, you can use setInter-

val( ) to call a function or method after a certain amount of time. The function or

method can be called once or many times at regular intervals. In the onAppStart( )

method in Example 4-3, setInterval( ), is called and passed a reference to the listCur-

rentUsers( ) function:

setInterval(listCurrentUsers, 60000);

In this example, listCurrentUsers( ) is called once every minute (60,000 milliseconds).

In turn, listCurrentUsers( ) iterates over the

application.clients array and calls each

client’s user.getConnectionInfo( ) method. This method uses the properties of the

client object, its user object, and User class methods to output text about the client.

See Macromedia’s Server-Side Communication ActionScript Dictionary (available in