ActionScript 3.0 :: Upload File And Get Info From Server Simultaneously

I want to upload file and get some information from server at the same time. I have the code:
file.addEventListener(Event.COMPLETE, function():void {
trace("complete 1"); });
file.addEventListener(DataEvent.UPLOAD_COMPLETE_DATA, function():void {
trace("complete 2"); });

When the returning data is not empty, I see:
complete 1
complete 2
But when the returning data is empty, I see:
complete 1
How can I understand that file uploading is compete absolutely even if received data is empty?