At the moment, we can't specify an interface without knowing its IP, which makes it difficult to listen on eth0 and not wlan0 for example. The exact same code should apply to the mDNS listener and the server.

Could also add this to the GUI and let the users select which interface to listen on, which interfaces to use for mDNS (and reverse-mDNS and which ports to use)

Printing and sound do not work properly as it is (sound is unreliable and unsafe - printing does not work on win32..) So just disable the options until we sort this out.

All session types should have a startup timeout which will check that the session has moved past "starting" state within 30 seconds. Some do, but not all apparently (or at least not in all cases). At least we now detect SSH errors and report them to the client.