Implement VOIP in iPhone and iPad

Does anybody is aware of implementing VOIP feature in iPhone and iPad.

The things for which i need clarity is,

1. By using which third party library/protocol can I implement this feature? Or is there any in built classed available in objective-c which I can make use of?

2. Is there any Apple store accepted iPhone application which uses VOIP implementation? If so where can I get implementation details of it.

3. This is a generic question. Can we use any third party's in our iPhone applica开发者_C百科tion or do we need to get any special permission from Apple reg the usage of third party's used.

Please let me know if needed more details reg this.

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pjsip library has been ported to iPhone. Checkout pjsip.org

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1.Yes you can implement using third party libraries like pjsip and linphone which provides example source code also.

2.Apple will not reject VOIP apps Check this iPhone app Links

https://itunes.apple.com/in/app/dial91-voip/id445578908?mt=8 https://itunes.apple.com/us/app/linphone/id360065638

3.I think no need to take permission from apple to use third party.