Whenever one googles for VoIP and iOS there's always a lot of results that appear that tell you about using CallKit. However CallKit on its own is useless, it just provides a GUI/OS integration of VoIP, but not the actual SIP nor VoIP things themselves.
There's lots of 3rd party libraries out that, however they all include licensing, or paying a fee, and are tied to the 3rd party's servers.
Approximately how much effort is it to develop from scratch in Swift code to enable an app to receive VoIP calls (it doesn't need to make outgoing VoIP calls, and and only audio, not video needs to be supported).
Here's what I think would be involved:
- Send information from the app to a SIP registrar. How difficult is this?
- Enable VoIP push handling in the app, send the Voip Push token to a server. Handle incoming VoIP push.
- Implement the VoIP transport, audio handling etc., for incoming VoIP
- Integrate with the OS
I know how to do 2, and for 4 there's loads of tutorials on CallKit.
What I'd like to determine is what is involved and a level of effort for implementing 1) and 3) without using a 3rd framework.
Anybody done this themselves and has a rough idea?