File sending over Jingle (with in-band-bytestream transport) has now been integrated into the UI. This has fortunately been quite easy as Dino already had support for file sending, via HTTP uploads. Thus I only needed to hook into the existing UI to also offer Jingle file transfers. This means that now you can click on the “attach” paper clip to send a file. Since prioritization of different transport methods and file receiving haven't been implemented so far, these changes aren't in the master branch yet.
Prioritization is important so that HTTP file uploads are preferred where possible (file small enough, server supports it): Jingle file transfers only work to a single target and only when it is online at the same time as the sender.
Since the ability to receive files via Jingle can also be reasonably expected if the client supports sending them, we basically have two blockers for merging.
Above you can see the chat window after some testing. ;)