I see that apps like facebook for example are getting push notifications in real time. When someone writes a message to me from a pc ill get the message to my android device as push notification just a second later even when my facebook app is not running.
Im wondering how it works because for my app i need a quite similar behaviour. There is also a messaging and an alert mechanism between server and client but i cant imagine how i could implement it so that i can get real time updates from the server to the client even when the app is not started.
Does someone know?