I'm writing an application that sends files over network, I want to develop a custom protocol to not limit myself in term on feature richness (http wouldn't be appropriate, the nearest thing is the  bittorrent protocol maybe).
I've tried with twisted, I've built a good app but there's a bug in twisted that makes my GUI blocking, so I've to switch to another framework/strategy.
What do you suggest? Using raw sockets and using gtk mainloop (there are select-like functions in the toolkit) is too much difficult? 
It's viable running two mainloops in different threads?
Asking for suggestions
Disclaimer: I have little experience with network applications.
That being said, the raw sockets isn't terribly difficult to wrap your head around/use, especially if you're not too worried about optimization. That takes more thought, of course. But using GTK and raw sockets should be fairly straightforward. Especially since you've used the twisted framework, which IIRC, just abstracts some of the more nitty-gritty details of socket managing.
networking application and GUI in python