There are two applications that I'm building. I need to implement calling from one application to another. How can I implement that ?
Basically, user on app1 should be able to call user on app2. It's like how UBER customers can call UBER driver app using internet. I'm using firebase as a BaaS.
Please mention links to relevant articles and tutorials.
I'd suggest Jitsi.org. It has a great API (simple VoIP and Video call can be achieved with just a couple of lines). It's open source and you can host your own private Jitsi server if required.
If you want the SDK to handle incoming calls etc. I'd suggest Vonage (TokBox) or QuickBlox.