How to make a IP based Chat app using MERN stack, and also the system design for such an app

How to build a ReactJs Chat App that allows you to chat with anyone who is connected to the same Wifi using Ip address as the identification field.

Should i store the chat history in a database?

Does the ip address of a device change on disconnecting and reconnecting to the same WIFI?

If u can help me it would be a great deal for me cause i certainly feel confused on how to implement it.