What you are looking for is local peer-to-peer file sharing. When I was studying, we used eMule, but that is for Windows and old. I don’t have a concrete software suggestion, but looking around the gnutella protocol could be promising.

Edit: QuantumCogs suggestion is also good, the use cases are slightly different.

Maybe make it look like a spam email? :-)

Write a web server with a countdown that sends you regularly a link via email to reset the countdown.

You could use React Native, so the language would be Javascript / Typescript.

It’s a series of numbers from a TV show called Lost.

https://en.wikipedia.org/wiki/Mythology_of_Lost#The_Numbers