Xcode 5 app submission issue
It might have been a coincidence, but like other recent xcode issues I solved this by restarting xcode.
For me the solution was to submit the app via Application Loader (downloadable directly from iTunes Connect) rather than Xcode.
I have the observation that with Mavericks and App Nap enabled, a hidden Organizer window within XCODE will cause the network connection to be dropped.
Even if the window is occulated (hidden) for just a second).
Make sure the window is always visible and the problem does NOT occur.