I would like to introduce a advanced usage of AMF48.
Following is a way to connect from Flex to Google App Engine(Java) by AMF.

**Client(Flex): Send a request.**

var commandAmf:ByteArray = new ByteArray();
commandAmf.writeObject(command);

var request:URLRequest = new URLRequest(COMMAND_URL);
request.method = URLRequestMethod.POST;
request.contentType = "application/x-amf";
request.data = commandAmf;

var handler:EventHandler = new EventHandler(command, callback);
var loader:URLLoader = new URLLoader();
loader.dataFormat = URLLoaderDataFormat.BINARY;
loader.addEventListener(Event.COMPLETE, handler.completeHandler);
loader.addEventListener(IOErrorEvent.IO_ERROR, handler.failHandler);
loader.load(request);

1. Construct a command, which has parameter of the request.
   (Omitted in above source)
2. Write command as AMF by ByteArray.writeObject()
3. Create a URLRequest which has URL of GAE, and set data.
4. Create a URLLoader, and send a request by load().

**Server(GAE): Decode command and exetute.**

protected void doPost(
        HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {

    // Decode Parameter.
    ICommand<?> command =
            AmfUtil.decode(req.getInputStream(),   ICommand.class);

    // Command Execution.
    Object data = command.execute();

    // Result.
    byte[] result = AmfUtil.encode(
            new Result(data, Result.SUCCESS, null));
    resp.setContentType("application/x-amf");
    resp.setContentLength(result.length);
    resp.getOutputStream().write(result);
}

1. Decode request as ICommand.
   (※ICommand is the interface, which has only execute() method.)
2. Execute the execute()  method of ICommand, and get the result.
3. Store result data into Result instance and encode Result as AMF to return.

**Client(Flex): Get the request result**

public function completeHandler(event:Event):void {

    var resultAmf:ByteArray = ByteArray(event.target.data);
    var result:Result = resultAmf.readObject() as Result;
    if (result == null) {
        result = new Result(null, -2, "No Result.");
    }
    callback(this.command, result);
}

public function failHandler(event:IOErrorEvent):void {
    var result:Result = new Result(null, -1, "Connection Error.");
    callback(this.command, result);
}

1. Get the Result by ByteArray.readObject().
2. Execute callback function.

#Following file contains above source files.
AMF48-GAESample