Push notifications will allow the softphone to wake-up on incoming call or chat even if the device is sleeping or the app is closed.
The Android softphone already has a built-in FCM profile which should be fine for trial usage however, for more serious production usage you might configure your own project.
Firebase Cloud Messaging (FCM) is a free service by Google.

Step by step instructions:

1. Log in to the Firebase Console at https://console.firebase.google.com
2. In the Firebase console, click Add project, then select or enter any project name
3. Click "Continue" and skip or setup Google Analytics
4. Click on "Create Project" and the "Continue"
5. In the center of the project overview page, click the Android icon to setup your project
6. Enter the correct Android package name!!! This will be set to com.companyname.brandname.app (normalized with all special characters removed)
7. Click on "Register App" and then download the google-services.json.
8. Upload your google-services.json file to the softphone builder web service.
9. The API key can be found at Project Settings -> Cloud Messaging tab -> Server key

There are multiple ways to handle push notifications:

1. Disabled: set the "enablepush" parameter to 0 to disable push notifications
2. If you don't configure any google-services.json and API key: push notifications can be handled by our push-SIP service using our Firebase profile
3. If you configure the google-services.json (but not the API key): push notifications can be handled directly by your server (if it has push support)
4. If you configure both google-services.json and API key: push notifications can be handled by our push-SIP service using your Firebase account

More help:

• https://firebase.google.com/docs/cloud-messaging/android/client
• http://alphatech.technology/Howto-Entry-srk/Google-Services-Json-bek/
• https://medium.com/@inspireui/setup-firebase-cloud-messaging-fcm-push-notification-for-flutter-apps-8c767fe64e54