Firebase Cloud Messaging - How to validate Tokens?

Question

I am using Firebase Cloud Messaging (FCM) and as per the abreviated code below everytime a new Token is generated on the Customer Device... I send this new TOKEN to my SERVER DB (Cloud) where I save it in order to be able to send future Push Notification from the Server to the Device using the CFM API.

    //public class CFMInstanceIDService extends FirebaseInstanceIdService ...      public void onTokenRefresh() {         ...         String cfmToken = FirebaseInstanceId.getInstance().getToken();                 ...              sendRegistrationToServer(customerGuid, cfmToken);     } 

By doing this I have on the Server a list of ALL (multiples) Devices where a Customer is logged-in. (Tablet, Phone, iPhone, Android, etc)

Is there any way to verify/validate a Token at any time?

I would like to know/ensure that all the tokens that I have associated to a Customer belong to real Devices. I don't want to send Push Notifications to not-existing Tokens.

Answer 1

Here is an example curl request that shows how to validate a token without actually having to send a message:

curl -H "Content-Type: application/json" -H "Authorization: key=$FCM_API_KEY" https://fcm.googleapis.com/fcm/send -d '{"registration_ids":["$FCMTOKEN"]}' 

Example invalid response:

{"multicast_id":7452350602151058088,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]} 

Example valid response:

{"multicast_id":9133870199216310277,"success":1,"failure":0,"canonical_ids":0,"results":[{"message_id":"0:1502817580237626%f590ddc2f9fd7ecd"}]} 

I got this answer from google's firebase support team.

Answer 2

Actually there is a workaround, you can use dry_run = true

This parameter, when set to true, allows developers to test a request without actually sending a message.

firebase docs

if user unsubscribe, you have a response with NotRegistered but real sending won't be performed