How to implement a completely private network on Ethernet from two devices?

Question

Electronics

I want to implement a completely custom network between two assembled devices. How I imagine it:
1. Implement 1 device (let's say it will be a transmitter)
2. Implement 2 device (let's say it will be a receiver)
3. Program (some kind of cancer?) microcontrollers on these two devices for I / O data
4. Connect RJ45 cable (UTP)
5. *Hopes that all this will take off (I hope not to heaven)*

And here are the questions:
1. How bad is it?
2. How all the same it to implement? (I know how the Ethernet protocol works, in principle, you can read the RFC)

The bottom line is to make a bicycle, but with its own blackjack and microcontrollers. That is, I want to buy some microcontrollers, solder this whole thing, implement the Ethernet protocol (at this stage, I remembered that the device should also have a MAC address * sukaaaa *) and connect with a twisted pair cable. Where to look so that it can be designed.
If there are variances, then we can offer a more simplified model, I just want to somehow implement protocols and TCP / IP, etc. in the future.

PS I know a bit how information is encoded.
And I don’t want ready-made modules, I just want to implement these modules

Answer 1

2 phu and they themselves will agree on everything.

Answer 2

If you have these 2 devices that support the exchange, you need to ping the device address, then as an option, if you own LabVIEW + VISA TCP / IP

Answer 3

It is possible to organize communication at any network level, the MAC level may be quite enough, and even easier for microns.