> within 5 mins from the sender initiating the send?

Based on a strict reading of the readme you actually need to receive in the same 5min window. This means that you have at most 5min. If you send at the end of the window you can have less than a second.

A simple solution is to have the sender always round up (to the end of the current 5min window) and have the receiver search for windows rounded up and down. (Or have the sender broadcast two and the receiver look for one)

If you want more time the sender can keep broadcasting a new window every 5min until the receiver connects.