What's the use of sendMessage method? Can I use it send push notifications to a particular device?

[joshiprashanthd]

I am working on notification system where a user on app1 does something and user on app2 gets notification of it. I tried to use the code from flutterfire's firebase_messaging examples.

Future<void> sendNotificationToListener(String listenerId) async {
    final user = await _firestoreService.readDoc('user_internal', listenerId);
    final token = user.data()!['fcmToken'];

    final data = {
      "routeName": "events-view",
      "title": "Scheduled",
      "body": "${_userService.user!.username} scheduled meeting",
    };

    try {
      final body = _constructFCMPayload(token, data);
      print(body);
      await http.post(
        Uri.parse('https://api.rnfirebase.io/messaging/send'),
        headers: <String, String>{
          'Content-Type': 'application/json; charset=UTF-8',
        },
        body: body,
      );
      print('FCM request for device sent!');
    } catch (e) {
      print(e);
    }
  }

  String _constructFCMPayload(String token, Map data) {
    return jsonEncode({'token': token, "data": data});
  }

But I am not getting any notification on the app2 I don't know why this happening. Is there something wrong with the url (https://api.rnfirebase.io/messaging/send)