Question Client Based Server

I have a multiplayer project.
the network topology of project is to connect all clients to the one of the players machine and not using cloud services.
In other words i want to make a player device as server and connect others to that device.




Notes:
i know that i still have to use a cloud server although weak.
i don't want to use relay.
i know that i must bypass the NAT, but i don't know how.
internet says that i have to use techniques like NAT puncthough , UDP hole punching, STUN, ICE, ... but no one says how to do that.