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I was thinking the same thing, the only difference from what I can tell is that the Facetime can connect to people with iPhones.
 
Facetime can receive calls while closed (as long as your Mac is connected to the internet, of course).

Does anyone know how this happens? Is there a process running in the background that is constantly connected to the internet?
 
Does anyone know how this happens? Is there a process running in the background that is constantly connected to the internet?

There's a ApplePushService.framework included in the package of the app, so I'm going to say yes there is a process that constantly runs in the background which turns the app on when you get a call. Just a guess though, I'm no expert.
 
oh wow, that's cool. But... why didn't they introduce that idea into iChat? and what are the limitations? Can I call my china iPhone owners for free?
 
oh wow, that's cool. But... why didn't they introduce that idea into iChat? and what are the limitations? Can I call my china iPhone owners for free?

It uses a data connection. So long as your china iphone owners have wifi then yes.
 
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