I'm an android developer and currently developing an app which requires device to device messaging. I'm new to FCM and so not sure about how to implement it completely. I've implemented the client side code (in Android Studio) but need help to implement server side code. I'm aware that this can be done by cloud platforms like Google Cloud Functions, but curious if I can achieve it via my own server too. That's why I decided to hire a freelancer to do this job.
My exact requirement : I have 2 apps, one for admin and one for customers. Every customer should be able to send push notifications to admin from the app, and similarly, an admin can send push notifications to all the users