Just this past weekend, I created a service for transferring files that is built on websockets (https://qr.dibble.codes / https://github.com/acdibble/qr-transfer). It's still rough and very MVP, but it's functional.

My use case was I wanted to transfer a PDF to an Android-based tablet but in the moment didn't want to log into my email. I couldn't think of any quick, easy, and cross-platform solutions so I decided to write the service.

It's built on socket.io which is a godsend for websockets because it automatically handles so much grunt work and your app just works.