WhatsApp. How it works?

Question

My friend recently downloaded WhatsApp to his Iphone. Anyone can tell me technically how it works? Does it use the same technology as PushMail? How can it stay in the background? I am not a Iphone Developer, btw.

Answer 1

I haven't used it but it looks like it is using APNS. This allows you to display notifications even though the app is not running

Send a message with text that lets the user launch your app. Trigger audible alerts with your own custom sounds