This is a program for sending a file from one computer to another using the nacl library. It is just written for learning and fun (think of is as crypto-fanfiction) so please do not consider it any more secure than sending a file in plaintext. If you wanted to do that use ssh or https or something like that which was written by experts, properly audited and has had time to be proven.
Before using it you should study each test file in order and the protocol documents.