How to deal with very high number of TCP connections at the same time:
http://www.kegel.com/c10k.html
TCP Server with GUI to debug tcp connections.
https://github.com/AlexxNB/TCPServerGUI
https://squidarth.com/article/networking/2020/05/03/tcp-resets.html
https://robertovitillo.com/what-every-developer-should-know-about-tcp/