Handle network resets, add restart button

[Nedehf]

When transferring a large file, while the transfer was active, the host lost connection with the router and stopped sending the file.

There was no error either on the host side or client side, but the worst in this situation (It was 90% complete) is that I had to start over given that once the connection was restored, there was no way to restore the connection

[robinkarlberg]

Hi, the functionality to restart a download is not implemented yet, but is on the TODO-list. The error messages are something that is to be worked on as well. When the time comes I will fix both.