Maybe this is the wrong feed or maybe this could function as discussion but I would really like to know about how to start and set up an online multiplayer game.

Over the years besides backend development I got more and more into game development and I learned Unity (2D stuff exclusively) eventually but fortunately a buddy of mine turned me on to Pico-8 which is where I finally really learned how games work and how they are supposed to be made - as I think. Now I am digging up C based card games I programmed years ago and I would like to set up an online card game framework to apply those games to - does not necessarily mean that I must use the actual C code. Any ideas/advice on how to get something like that to work and furthermore be reusable?

I appreciate any kind of answer or advice since I am a total rookie.

Thanks in advance! (: 

Cheers!