I have a doubt, when we try to register for C2DM, does the registration happens in backgroud thread or in normal thread. Thanks in advance
It is done through an Intent, but when google changes your registration id, you need to have a broadcast receiver to handle the new registration id. When you get the new one you need to send it to your 3rd party server to make it able to send message to the phone. As @Jay Thakkar said, Vogella's article is quite nice tutorial for understanding the c2dm.