Build a VoIP Call App with CallKit in iOS

In this tutorial, we have covered how to implement VoIP functionality in an iOS application using CallKit and PushKit. We started by setting up the development environment and creating a new Xcode project. Then, we installed Firebase and configured it for our app. Next, we implemented push notifications using APNs and Firebase Cloud Messaging (FCM). After that, we created a VoIP service extension to handle incoming calls when the app is in the background or suspended state. We also implemented logic to manage call acceptance or rejection from the remote user. Finally, we tested our implementation by running the application on an iOS device and simulating incoming calls.