How to use Push notification in android using JSON protocol?

I am new to push notification and i dont know how to use it in android. So at first please give me idea about 开发者_C百科push and then how to use JSON protocol in it.

The app sends PUSH notification to the user via JSON protocol.

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http://blog.mediarain.com/2011/03/simple-google-android-c2dm-tutorial-push-notifications-for-android/ here you go,

but push notifications are android 2.3+ as far as i know...