Live connection Voip in Background for iPhone

I'm updating one voip application and one of my issue is supporting multitasking. I don't know how I should manage multitasking. Specially I need define connection as VoIP, to receiving incoming call when app is in background, but I don't know how do that.

开发者_运维知识库

I searched and found This tutorial and a lot of other pages, but I could not found how those work. Is any one able to explain me it?

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Apple only allows you to set up a TCP connection that you can handle with a CFNetworkStream. You need to bind the socket to a CFNetworkStream and then set the handler to the kCFNetworkStream value that enables VoIP. You'll need to support TCP to handle the socket as Apple doesn't support backgrounding over UDP. The documentation provided by Apple is quite clear on what you can do.