How to make Backdoor for a server?

Hey, I'm really new to hacking Gmod but I found a tutorial on here that gave me a bypass.lua, and external.dll, I also found an Odium menu on here but can't use it unless there is a backdoor to a server, so I'm wondering, how can I make a backdoor? I don't know if this is legit but I found this tutorial online, if its true than could someone please explain it to me, if not can someone teach me how to make a real one?

Video I found: https://www.youtube.com/watch?v=GFk9VKsbRbc

Thanks!

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Backdoor Example (Simple way & With Server-to-Web connection):
https://www.mpgh.net/forum/showthrea...1#post14863681