https://github.com/twilio/twilio-aspnet
https://github.com/plivo/plivo-dotnet
https://gitlab.com/naxam/sinch-rtc-ios-binding/tree/master
https://github.com/NAXAM/sinch-rtc-android-binding
https://github.com/Nexmo/nexmo-dotnet
Could not add Nexmo.CSharp.Client. See commit https://github.com/fritzlim/VoipAndMessagingTest/commit/c125fe7d9c2f8b9ed5cceae8ba8c592660f632dc description.