Send notification from web to android device using Firebase - asp.net-mvc

Question

I am trying for a while now to implement this flow: When user adds some files on server app, notification should trigger and send from server to FCM and that from there to pass message saying something like: 'New file has been added'.
Basically I want to inform mobile device user that something on server has been changed.
I have tried many things, but nothing seems to work as I would expect, at least.
On the mobile side I have set up Firebase inside my Xamarin.Android project, and when I am sending notifications directly from Firebase console, I get notifications, and everything is good.
But I don't want to send notifications via Firebase console, I would rather send notification from server (which is ASP.NET MVC project) to Firebase console and then pass it from there to android device.
My first question would be: Has anybody got an idea how can I inform web app about device_id? Is there some way that android device send this information on server? And maybe from there I can store that data and update it occasionally, since it is basically a refresh token.
My second problem is this: Even when I hard code current device_id of an active android device and try to send a message from server whit this code:
public class FirebaseService : IFirebaseService
{
public void SendMessageToClientApplication(string message, string serverApiKey, string senderId, string deviceId)
{
AndroidFCMPushNotificationStatus result = new AndroidFCMPushNotificationStatus();
try
{
result.Successful = false;
result.Error = null;
deviceId = "eMk6mD8P8Dc:APA91bG5Lmqn4Hwb4RZJ1Mkdl8Rf_uYQsQCEfDJK334tzSvIGzdao7o2X6VmtcTEp_Li0mG8iUoUT7-_RnZxQKocHosZwx6ITWdpmQyCwUv60IIIy0vxNlEaccT6RqK6c-cE1C6I3FTT";
var value = message;
WebRequest tRequest = WebRequest.Create("https://fcm.googleapis.com/fcm/send");
tRequest.Method = "post";
tRequest.ContentType = "application/x-www-form-urlencoded;charset=UTF-8";
tRequest.Headers.Add(string.Format("Authorization: key={0}", serverApiKey));
tRequest.Headers.Add(string.Format("Sender: id={0}", senderId));
string postData = "collapse_key=score_update&time_to_live=108&delay_while_idle=1&data.message="
+ value + "&data.time=" + DateTime.Now.ToString() + "&registration_id=" + deviceId + "";
Byte[] byteArray = Encoding.UTF8.GetBytes(postData);
tRequest.ContentLength = byteArray.Length;
using (Stream dataStream = tRequest.GetRequestStream())
{
dataStream.Write(byteArray, 0, byteArray.Length);
using (WebResponse tResponse = tRequest.GetResponse())
{
using (Stream dataStreamResponse = tResponse.GetResponseStream())
{
using (StreamReader tReader = new StreamReader(dataStreamResponse))
{
String sResponseFromServer = tReader.ReadToEnd();
result.Response = sResponseFromServer;
}
}
}
}
}
catch (Exception ex)
{
result.Successful = false;
result.Response = null;
result.Error = ex;
}
}
}
I get nothing both in Firebase console and of course nothing on device as well.
I have tried to implement Firebase web as javascript on my server app like this:
<script>
var config = {
apiKey: "mykey",
authDomain: "myauthdomain",
databaseURL: "mydatabaseurl",
projectId: "myprojectid",
storageBucket: "mystoragebucket",
messagingSenderId: "mysenderid"
};
window.onload = function () {
firebase.initializeApp(config);
const messaging = firebase.messaging();
messaging.requestPermission()
.then(function () {
console.log('Notification permission granted.');
return messaging.getToken()
})
.then(function (token) {
console.log(token);
})
.catch(function (err) {
console.log('Unable to get permission to notify.', err);
});
messaging.onMessage(function (payload) {
console.log('onMessage: ', payload);
});
}
</script>
But this code gets some kind of a different device_id(aka token), probably one generated for that server machine.
Does anybody has experience with sending device_id to server app and from there sending notification message to Firebase console? I would appreciate some code examples, tutorials or anything that can help, since I was unable to find something useful during my google search.

Answer 1

My first question would be: Has anybody got an idea how can I inform web app about device_id?
The most common approach is to store the list of device tokens (each device that uses FCM has such a token) in a database, such as the Firebase Database. There is an example of this in the Cloud Functions for Firebase documentation. In this example the devices receiving the messages are web pages, but the approach is the same for iOS and Android.
I also recommend reading Sending notifications between Android devices with Firebase Database and Cloud Messaging. In this article, instead of sending to a device token, each user subscribes to a topic. That prevents having to manage the device tokens in your code.