How to make instant online alerts in android app?

Question

Android

It is necessary to add functionality to the application so that an alert with the necessary information instantly appears on all smartphones with this application. By analogy with the VKontakte application, when a message arrives, an alert is displayed. In my application, I also need to trigger a similar alert.
Please direct to the right sources, guides or documentation on how such things are organized.

Answer 1

I can advise you to look for " implementation of push notifications on android ", I myself do not really understand this, but you need to look exactly in this direction.

Answer 2

In addition to sending and receiving push notifications, you will need to deal with local notifications.