Hey Don,
Connections as you are thinking of them do not exist for UDP. At the heart of it you only ever send a packet and listen for packets. i.e There is nothing stopping you from sending a packet to a destination that is not listening.
After you have stopped listening do you recreate the udp listener or attempt to reuse an existing one?
Also it is a very odd use case to open/close/open the same listening port again, any chance you could give me some insight into what you are trying to achieve?
Regards,
Marc