var req:URLRequest = new URLRequest();
var loader:URLLoader = new URLLoader()

req.url = 'receiver.php';
req.method = URLRequestMethod.POST;
req.contentType = "multipart/form-data, boundary=" + multipart.boundary;
req.data = multipart.data;

loader.addEventListener(ProgressEvent.PROGRESS, _onProgress_upload);

loader.load(req);


function _onProgress_upload(e:ProgressEvent):void {
    trace('* _onProgress_upload : ' + [e.bytesLoaded, e.bytesTotal]);
    //* _onProgress_upload : 18,18
}