Rainmaker android app

[Halabdelkrim]

Hello,

I'm trying to use the ESP Rainmaker example as a core of my project, but i'm a very beginner in developing Android apps with Java language.

I want to add more functionalities to the app, but i'm confused how to modify the ESP Rainmaker android app to send a custom message (JSON format) to the ESP32.

Which function/method should i use to send custom messages to the ESP32?

It would be so appreciated if you can provide me with an example of it, or at least a starting point from where i can go.

Thank you.