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.

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

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.