1. Go to -> https://console.firebase.google.com/ Login and create "new Project".
2. https://ibb.co/TWtf7Dc go project settings page.
3. Create "app.js" and "firebase-messaging-sw.js" file with 2.step information.
4. Don't open your application like adress "192.168.1.XXX:8088". You open adress like "127.0.0.1:8088".

You can send a notification to your application using the "Postman" application.

1. Open Postman application.
2. Write adress https://fcm.googleapis.com/fcm/send
3. Chose POST method https://ibb.co/RTXKPCZ , https://ibb.co/WKSq2Tt

Goog Luck !