ActionScript 3.0 :: Detecting Bandwidth - Class Not Working

I'm trying to detect a user's bandwidth from my swf however, I have never used classes before so I'm all messed up. In the help file it says to do the following and when I do it gives an error of:

Quote:

1131: Classes must not be nested.

After reading the help file on Classes I don't understand why this below doesn't work when I put it in my fla. I have tried to put this in a separate file and save it as an .as and import it in but it didn't work.

ActionScript Code:
class Client {
public function onBWCheck(... rest):Number {
return 0;

[Code].....