depends on your needs, and your tolerance to latency.

anything TCP is simplest to deal with but it's much slower due to acks.

pure UDP is fast but unreliable, so most solutions involve some hybrid of the two.

ENet or RakNet work just fine for many general applications - the question becomes, if a client loses connection due to wifi/unstable connection, how do you resync them? If it's a shooter, you need a way to know who was right (latency compensation), so it quickly becomes a complex problem. In fact, a simple web socket library can probably handle a lot of use cases, it's more about how you deal with sessions, latency, etc that's application specific and can be challenging.

Some games go as far as to have the server replay the simulation to know the ground truth of what really happened.

The most basic form of a game server is just message passing really.

My game Stemwater Spades features a fully implemented lobby, client server model, and authentication with a central login server, and it never trusts the client. It has its own message system. You can use something like protobuff but I enjoyed doing it myself It might be helpful:
https://github.com/jmasterx/StemwaterSpades/blob/master/Spades%20Game/Game/Net/ServerCore.cpp

you can branch around from there, there's a lot of files.

If you have questions about the code, I might remember how it works but it's been a while

Nice. Did you get a commit on ENet?

To be completely honest, I'm still not 100% on TCP, HTTP, and TLS (are there any others?).

My thought, was that TCP was the fire-it-and-forget-it message type. That's the one I'm going for. I can figure out alternative ways to make those data packets sync and communicate, so I don't want to get more complicated than that.

Interesting. I always thought TCP (was|would be) the fastest. I tried it over an ngrok connection. It's a lot slower than I expected. localhost speeds is basically what I'm looking for.

Ok. That sounds good.

Alright, I have a really cool breakthrough for sure. I managed to pull my old https://github.com/MarkOates/flare_network project and built without error right out of the box on my Mac.

I converted the project and removed the boost dependency. Now, the dependency is only a cloned repo of asio. It builds on Windows now, too (but I have a problem with the client executing, keep getting a "Exception: resolve: No such host is known." on win when not using localhost). So major progress. Definitely usable primitives to do what I plan to do.

It's basically a silent server program (shows connect and disconnect messages when running) that relays basic messages, and a client program that you type into std::in and after pressing ENTER, will send the message to the server. The client also receives and outputs all messages relayed from the server.

I've tried it on localhost (works on Mac and Win), and tried it connecting over a ngrok tcp tunnel (works on Mac). I had my laptop sending messages to my MacMini and vice versa. Next steps would be to componentize the class, and extract it from the entry point main, and add tests.

Legit though, I'm drinking a glass of wine to this. I consider this a huge success.

HTTP/HTTPS and TLS are protocols over TCP IP.

Okay Mark:

TCP-IP is the transport protocol. Anything else on top of it is using basic connect/accept send/recv.

HTTPS/SSL are encrypted protocols over tcp ip. What I stated before is true.

For your needs you'd better stick to enet/known equivalent or even parts of my lib. You can cannibalize it to just use what you need.

Let's warn you: cross platform networking and encapsulation are pains. When you'll be there we will talk about dead reckoning algorithms and such.