Form Listing Failed!

Hi every one.
I want to use Virtual Box as Aggregate server . everything in computer and browser is Ok but when I want to connect server by ODK collect I encounter an Error that say "Form Listing Failed. with connect to" .
Help me please .

I am not able to reproduce your problem, mine aggregate vm works fine with Collect, I am able to Get blank Form and sent submission as well. I am not an expert of course but what is very interesting for me in the screenshot that you attached is that in the browser there is no port number:

So are you sure that you input a correct URL address as a server on the Collect?