Question

I am trying to make an app that connect to the server.
The app is used by some devices.
If one of the devices upload something to the server, I would like other devices receive the notification about the server has something new.
My question is, how to check the server is change or not? How often we must check the server?
I wonder how the Online Messaging work, because someone send something, we receive the message ASAP
Is the concept can be use with my app?

Answer 1

Sounds like you want to take advantage of Google Could Messaging or GCM for short.

http://developer.android.com/guide/google/gcm/index.html

This could be a lightweight message telling the Android application that there is new data to be fetched from the server (for instance, a movie uploaded by a friend), or it could be a message containing up to 4kb of payload data (so apps like instant messaging can consume the message directly).

GCM is the standard for how your apps “talk” to your servers. Either for a message in it’s entirety or just a message to go check the server because it’s been updated.