Install libsodium on your dev environment. Either by following
https://doc.libsodium.org/installation
or by sudo apt update and maybe
sudo apt install libsodium-dev build-essential g++ autoconf autotools-dev
make
make run1
make run2 in another terminal
You’ll have debug information printed to the screen so you’ll be able to follow the logic. Enter some words in the terminal to see them be encrypted and sent over to the other running instance.