Firebase Topic Messaging always return InvalidRegistration error when push notifications in ASP.NET

Question

I am developing an Asp.NET MVC application. In my application, I need to push notifications to Android Devices using Firebase. This is the consequence of this question - https://stackguides.com/questions/40416654/unable-to-push-firebase-notifications-to-multiple-devices-using-webclient-in-asp I asked.

After I searched for solutions, I realized that I should use Topic Messaging of Firebase - https://firebase.google.com/docs/cloud-messaging/android/topic-messaging. But when I use topic messaging and push from server, it always return Error=InvalidRegistration error.

I subscribe to a topic in Android like this

FirebaseMessaging.getInstance().subscribeToTopic("newsTopic");

Then I push like this in asp.net

public string PushNotifications()
        {
            using (var client = new WebClient())
            {
                client.Headers.Add(string.Format("Authorization:key={0}", Utils.FirebaseServerKey)); //get from firebase
                var values = new NameValueCollection();


                values["to"] = "/topics/newsTopic";
                values["data.message"] = "This is the test FCM test message";
                var response = client.UploadValues("https://fcm.googleapis.com/fcm/send", values);
                string responseString = Encoding.Default.GetString(response);
                if (!string.IsNullOrEmpty(responseString))
                {
                    return responseString;
                }
                else
                {
                    return "Something went wrong";
                }
            }
        }

But when I push, it returns this Error=InvalidRegistration.

Update

I tried replacing

values["to"] = "/topics/newsTopic";

with this

values["condition"] = "'newsTopic' in topics";

It returns, Error=MissingRegistration

Given that the code is almost the same as in your previous question and you get the same error message, this would be better as an edit to that question. — Frank van Puffelen

KVS KVS · Accepted Answer · 2017-07-04T23:28:35

I could reproduce the problem(Error=MissingRegistration) when I did not include "Content-Type=application/json" header. Can you try adding the Content-Type header?

Firebase Topic Messaging always return InvalidRegistration error when push notifications in ASP.NET

Update

1 Answers