Getting started with a VOIP app for iOS or Android?

Question

I'd like to create an app for iOS that does VOIP, presumably by interacting with a website. I can start with Android too.

Does anyone know of any tutorials, suggestions or libraries that would be of any use.

(The app would need to be rewritten for BB and android eventually, too.)

EDIT:

Bonus: What is SIP?

Answer 1

Well I'd suggest looking at the a SIP library that can work on Android. There are several SIP libraries out there for Java, but it's unknown if they work on Android.

There is a project that adds SIP/VoIP to Android:

http://sipdroid.org/

I'd check that out and see what they did to get the audio from the handset, and approach to implementing SIP, etc. You can't use that code for closed source development because it's GPL, and they are very clear about who can use it.

SIP protocol:

http://www.cs.columbia.edu/sip/

http://www.sipforum.com/

Hope that helps you get started.

Answer 2

These answers suggest using siphon.

SIP is the Session Initiation Protocol, a transport- and media-agnostic protocol for setting up, modifying and tearing down long-term associations between multiple parties. It's formally defined in RFC 3261.

Usually SIP is paired with the Session Description Protocol which describes the media streams the various parties wish to use. SIP uses an offer/answer model for the parties to exchange these media descriptions.

If you can possibly avoid it, don't write a SIP stack (unless it's for fun, of course). It's a LOT of work.