What to use for SIP calls from a mobile application?

Question

Android

There are:
- Mobile applications for iOS and Android;
- Asterisk 11 configured and visible from the Internet.
Needed:
- For users of mobile applications, add the ability to make calls to the operator via the Internet.
Perhaps there are ready-made libraries or code that can be "embedded"?

Answer 1

Perhaps (Android)\Phone\Settings\Accounts & Use Internet Calling ?

Answer 2

developer.android.com/guide/topics/connectivity/si...
iOS will be harder :)