How to implement Beluga or WhatsApp like messaging system in Android 2.1

Question

I am trying to develop a message app within my android app. The message will be like whatsapp and beluga. I googled it and found C2DM Android 2.2 can send the push notificat

Answer 1

For Android: Whatsapp is build upon C2DM and when the app opens it opens an XMPP connection to their service to deliver the messages instantly. They also might use MQTT as a protocol to minimize battery usage. That's basically it.

Edit: I learned more, Facebook uses MQTT in their messaging app. Whatsapp is build upon XMPP with their own extensions. Their server side runs on top of ejabbard (XMPP implementation in erlang). http://www.ejabberd.im/

On pre 2.1 devices WhatsApp probably keeps a connection open to their XMPP servers in the background but this is not really good for battery life.