If you just want to transfer files, you can use something like this:
Disclosure: Not my app. Just something I found during a quick google search.
If you want to build one out to sell or give as an android app, you will need to source out networking protocols. That would be beyond the scope of a forum discussion at this point in terms of detailing it out.
In the example given by @AppStudioSupport using Ajax calls, you will need to set up a server that picks up those calls and processes them.