Nostr - look at the library nostr-tools and ndk for some examples. 

https://github.com/nbd-wtf/nostr-tools

Relays - you can use nostream
https://github.com/cameri/nostream

Getting familiar with that stuff, reading+writing events and the command line will get you pretty far. 

 Thank you. I recently heard about nostream in video from Nostrica. I'll dive into what youve shared. 

 Also if you're looking for other projects

https://github.com/aljazceru/awesome-nostr