I am trying to implement a simple android app that has the ability to send device to device notification, like in almost any IM app exists.
In my app the implementation is even simpler, since there is only one user that receive notifications. All the other users can send them to him.
I am trying to find a solution for the last 10 days and so far I only found that it is hard do do it using Firebase Cloud Platform (since I need to implement my own server), and that it is maybe possible using oneSignal.
Have anyone done this before? Have anyone used oneSignal and can tell me if I can easily implement it without building another server?