Network low level works in unity for multiplatform game.

I wan’t to make multiplatfrom online multiplayer turn base game in unity, I’ll have my own server using NodeJS and i need some low level works like sending http requests or making simple tcp/ip networks and so on.
one friend told me about using UDP and TCP protocols with C# itself, but i think it’s not good way for multiplatfrom games as i like to have both android and pc version with same project and i think C# low level codes doesn’t work on android! ( maybe i’m wrong, I’m not sure about it ). in some game engines we have general low level functions or methods that works on all platforms, for example we write http_request(“URL”) and we don’t worry about what is target platform. do we have something like this in unity 2019?

I see “Unity Pro is required in order to build using .NET sockets”, is it right? so what should i use to make simple tcp network in free version of unity 2019?