I am trying to simulate a 'HEAD' method using UrlLoader; essentially, I just want to check for the presence of a file without downloading the entire thing. I figured I would just use HttpStatusEvent, but the following code throws an exception (one that I can't wrap in a try/catch block) when you run in debug mode.

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="init()">
<mx:Script>
    <![CDATA[

       private static const BIG_FILE:String = "http://www.archive.org/download/gspmovvideotestIMG0021mov/IMG_0021.mov";

       private var _loader:URLLoader;

       private function init():void {
            _loader = new URLLoader();
            _loader.addEventListener(HTTPStatusEvent.HTTP_STATUS, statusHandler);
            _loader.addEventListener(IOErrorEvent.IO_ERROR, errorHandler);
            _loader.addEventListener(SecurityErrorEvent.SECURITY_ERROR, errorHandler);
            _loader.load(new URLRequest(BIG_FILE));   
       }

       public function unload():void { 
            try {
                _loader.close();
                _loader.removeEventListener(HTTPStatusEvent.HTTP_STATUS, statusHandler);
                _loader.removeEventListener(IOErrorEvent.IO_ERROR, errorHandler);
                _loader.removeEventListener(SecurityErrorEvent.SECURITY_ERROR, errorHandler);
            }
            catch(error:Error) {
                status.text = error.message;
            }
        }

        private function errorHandler(event:Event):void {
            status.text = "error";
            unload();
        }

        private function statusHandler(event:HTTPStatusEvent):void {
            if(event.status.toString().match(/^2/)) {
                status.text = "success";
                unload();
            }
            else {
                errorHandler(event);
            }
        }   
    ]]>
</mx:Script>

<mx:Label id="status" />

I tried using ProgressEvents instead, but it seems that some 404 pages return content, so the status event will correctly identify if the page exists.

Anyone have any ideas?