If you're trying networking for the first time with itch there are 2 things I'd like to point out.
1. you have to use websockets. You can write you're code all the same as a normal networking project in godot, but just need to switch a couple of lines when you're done: this post should help you
2. Your server/client need to run over wss/https: this post and this thread should help you too assuming you already know how to host a server. GL!