Hi
There is currently no direct/streaming one-to-one file transfer right now. What you'd have do is upload to media server and share it on a private channel.
This is more like sharing with dropbox and it usually works better (e.g. laptop+mobile on receiving end, web vs. native app, resuming downloads, re-downloading due to corruptions or device switch, ....)
You can make it feel like a transfer by applying a custom UI (and some convention).
Or you could do a skype / firefox like UI with past downloads, showing if you have downloaded it on this device yet and a button to finally remove it from all devices by using ephemeral channels for file transfer.
PS: If you ever want to see why one-on-one file transfer gets tricky try to run skype on multiple machines and do some file transfer tests. It's not nice. BTSync or aerofs are doing direct transfers and work better but are still no fun to use (IMHO). The dropbox (or even owncloud) model just works, is easy to understand and very friendly regarding multiple devices, redownloads and alike.