There is small Xamarin App on Android hosting SMS Server written in FSharp and using the Suave library.
I use it to transform my old Android smartphones to SMS API endpoints for domotic and robotic personal projects.
- Download and install the APK from https://github.com/rflechner/SmsServer/releases
- You can connect your phone to your private WIFI network
- Run the app
- Tap on "Start server" button
- Go to the swagger API documentation