So it's not that you can't get something back but rather that you don't know how to send a properly formatted data to the server, right? I suggest you take a network sniffer and intercept a browser connection to the server handling the request and look how the data should be formatted. Alternatively craft an artificial server (like using netcat or a simple hand-written tcp server), get a form that uses multipart formatting, redirect it to your artificial server and use a browser to send such request. Then you'll know how the data should look like. Yet another way is to use a web search engine to find out how multi-part requests are formed.