How can I test if an URL is valid in Actionscript 3.0 ?

Question

Hy, everyone!
I`m trying to make a function that tests to see if an URL is
valid and return true if it is, false otherwise, so that I can use
it in an 'if' statement.
The way I try to do it is by using two event listeners for
the 'contentLoaderInfo' proprety of a Loader: one for Event.OPEN(if
this event is dispatched, then I know the URL is valid) and one for
IOErrorEvent.IO_ERROR(if this event is dispatched, then I know the
URL is not valid).
But the problem is that by using the event handler functions,
I leave the main URL tester function, and am unable to return a
value from it. The way I thought of to get around this problem was
to set a returnValue variable, to which to assign the return value
of the two event handler functions and then just go 'return
returnValue;'. But I don`t know how to return a value from a event
handler function, and even if I did I still couldn`t do it that
way, because it takes some time to dispatch those events and the
'returnValue' variable would be undefined by the time I try to
return it.
I hope you understood what I tryed to explain above... Here`s
some code to ilustrate this better(it`s not valid, it`s just so you
understand my problem):
private function testUrl(url:String):void {
var returnValue:Boolean;
var loader:Loader = new Loader();
returnValue =
loader.contentLoaderInfo.addEventListener(Event.OPEN, onGoodUrl);
// This is a global variable to which I assign the value of
'loader' so that I can close it from onGoodUrl
_testLoader = loader;
returnValue =
loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR,
onBadUrl);
loader.load(new URLRequest(url));
// Even if I knew how to make an event handler that returns a
value, I`d still have to wait for the loading to start, and I
couldn`t return the value here:
return returnValue;
private function onGoodUrl(event:Event):Boolean {
_testLoader.close();
return true;
private function onBadUrl(event:IOErrorEvent):Boolean {
return false;
You know any way to go around this problem? Or, for that
matter, do you know any other way to test for a valid URL?
Thank you for your time!

Answer 1

You need to test httpStatus of the URLLoader. Streaming
content undergoes a specific process when coming into Flash. The
only issue with httpStatus is that it does not work for every
browser....mostly Linux based systems and lesser programs on the
evolutionary food chain. I have not experienced problems with IE or
NS/FF on Vista at this point.
1. Send Request
2. Receive HTTP Status (HTTPStatusEvent.HTTP_STATUS)
3a. Status Good - Begin Load (Event.OPEN)
3b. Status Bad - 404 or Protected Filed
(IOErrorEvent.IO_ERROR)
4. Receive File - Downloading (ProgressEvent.PROGRESS)
5. Download Complete (Event.COMPLETE)