Onions:
Is there a way to achieve this, to either reboot the Nanode, or re-load the code which establishes a fresh connection?
avr watchdog timer - Google Search
Lots of ways! You'll want to set up a watchdog timer, then re-set it whenever there is a connection. That way, when the connection stops and the watchdog is not reset, it'll reset the actual board.
Onions.
What is the actual code to force a system reset?