diff --git a/app/src/main/java/com/github/gotify/service/Constants.kt b/app/src/main/java/com/github/gotify/service/Constants.kt
index 59bf7e2..40b6da8 100644
--- a/app/src/main/java/com/github/gotify/service/Constants.kt
+++ b/app/src/main/java/com/github/gotify/service/Constants.kt
@@ -1,14 +1,22 @@
 package com.github.gotify.service
 
 /**
- * Constants found here:
- * https://github.com/UnifiedPush/UP-lib/blob/main/src/main/java/org/unifiedpush/connector/Constants.kt
+ * Constants as defined on the specs
+ * https://github.com/UnifiedPush/UP-spec/blob/main/specifications.md
  */
 
-const val NEW_ENDPOINT = "org.unifiedpush.android.connector.NEW_ENDPOINT"
-const val UNREGISTERED = "org.unifiedpush.android.connector.UNREGISTERED"
-const val MESSAGE = "org.unifiedpush.android.connector.MESSAGE"
+const val ACTION_NEW_ENDPOINT = "org.unifiedpush.android.connector.NEW_ENDPOINT"
+const val ACTION_REGISTRATION_FAILED = "org.unifiedpush.android.connector.REGISTRATION_FAILED"
+const val ACTION_REGISTRATION_REFUSED = "org.unifiedpush.android.connector.REGISTRATION_REFUSED"
+const val ACTION_UNREGISTERED = "org.unifiedpush.android.connector.UNREGISTERED"
+const val ACTION_MESSAGE = "org.unifiedpush.android.connector.MESSAGE"
 
-const val REGISTER = "org.unifiedpush.android.distributor.REGISTER"
-const val UNREGISTER = "org.unifiedpush.android.distributor.UNREGISTER"
-const val MESSAGE_ACK = "org.unifiedpush.android.distributor.MESSAGE_ACK"
\ No newline at end of file
+const val ACTION_REGISTER = "org.unifiedpush.android.distributor.REGISTER"
+const val ACTION_UNREGISTER = "org.unifiedpush.android.distributor.UNREGISTER"
+const val ACTION_MESSAGE_ACK = "org.unifiedpush.android.distributor.MESSAGE_ACK"
+
+const val EXTRA_APPLICATION = "application"
+const val EXTRA_TOKEN = "token"
+const val EXTRA_ENDPOINT = "endpoint"
+const val EXTRA_MESSAGE = "message"
+const val EXTRA_MESSAGE_ID = "id"
diff --git a/app/src/main/java/com/github/gotify/service/PushNotification.kt b/app/src/main/java/com/github/gotify/service/PushNotification.kt
index cb5dc0a..43aac43 100644
--- a/app/src/main/java/com/github/gotify/service/PushNotification.kt
+++ b/app/src/main/java/com/github/gotify/service/PushNotification.kt
@@ -13,9 +13,9 @@ fun sendMessage(context: Context, application: String, message: String){
     val token = getToken(context,application)!!
     val broadcastIntent = Intent()
     broadcastIntent.`package` = application
-    broadcastIntent.action = MESSAGE
-    broadcastIntent.putExtra("token", token)
-    broadcastIntent.putExtra("message", message)
+    broadcastIntent.action = ACTION_MESSAGE
+    broadcastIntent.putExtra(EXTRA_TOKEN, token)
+    broadcastIntent.putExtra(EXTRA_MESSAGE, message)
     context.sendBroadcast(broadcastIntent)
 }
 
@@ -23,18 +23,36 @@ fun sendEndpoint(context: Context, application: String, endpoint: String) {
     val token = getToken(context,application)!!
     val broadcastIntent = Intent()
     broadcastIntent.`package` = application
-    broadcastIntent.action = NEW_ENDPOINT
-    broadcastIntent.putExtra("token", token)
-    broadcastIntent.putExtra("endpoint", endpoint)
+    broadcastIntent.action = ACTION_NEW_ENDPOINT
+    broadcastIntent.putExtra(EXTRA_TOKEN, token)
+    broadcastIntent.putExtra(EXTRA_ENDPOINT, endpoint)
     context.sendBroadcast(broadcastIntent)
 }
 
 fun sendUnregistered(context: Context, application: String, _token: String?){
-    val token = _token?: getToken(context,application)!!
+    val token = _token?: getToken(context, application)!!
     val broadcastIntent = Intent()
     broadcastIntent.`package` = application
-    broadcastIntent.action = UNREGISTERED
-    broadcastIntent.putExtra("token", token)
+    broadcastIntent.action = ACTION_UNREGISTERED
+    broadcastIntent.putExtra(EXTRA_TOKEN, token)
+    context.sendBroadcast(broadcastIntent)
+}
+
+fun sendRegistrationFailed(context: Context, application: String, token: String, message: String){
+    val broadcastIntent = Intent()
+    broadcastIntent.`package` = application
+    broadcastIntent.action = ACTION_REGISTRATION_FAILED
+    broadcastIntent.putExtra(EXTRA_TOKEN, token)
+    broadcastIntent.putExtra(EXTRA_MESSAGE, message)
+    context.sendBroadcast(broadcastIntent)
+}
+
+fun sendRegistrationRefused(context: Context, application: String, token: String, message: String) {
+    val broadcastIntent = Intent()
+    broadcastIntent.`package` = application
+    broadcastIntent.action = ACTION_REGISTRATION_REFUSED
+    broadcastIntent.putExtra(EXTRA_TOKEN, token)
+    broadcastIntent.putExtra(EXTRA_MESSAGE, message)
     context.sendBroadcast(broadcastIntent)
 }
 
diff --git a/app/src/main/java/com/github/gotify/service/RegisterBroadcastReceiver.kt b/app/src/main/java/com/github/gotify/service/RegisterBroadcastReceiver.kt
index 67021f3..7029978 100644
--- a/app/src/main/java/com/github/gotify/service/RegisterBroadcastReceiver.kt
+++ b/app/src/main/java/com/github/gotify/service/RegisterBroadcastReceiver.kt
@@ -30,7 +30,7 @@ class RegisterBroadcastReceiver: BroadcastReceiver() {
         }
     }
 
-    private fun registerApp(db: MessagingDatabase, application: String, connector_token: String) {
+    private fun registerApp(context: Context?, db: MessagingDatabase, application: String, connector_token: String) {
         if (application.isBlank()) {
             Log.w("RegisterService","Trying to register an app without packageName")
             return
@@ -46,12 +46,16 @@ class RegisterBroadcastReceiver: BroadcastReceiver() {
         // User should unregister this app manually
         // to avoid an app to impersonate another one
         if (db.isRegistered(application)) {
-            Log.w("RegisterService","$application already registered with a different token")
+            val message = "$application already registered with a different token"
+            Log.w("RegisterService",message)
+            sendRegistrationRefused(context!!,application,connector_token,message)
             return
         }
         val app = createApp(application)
         if(app == null){
-            Log.w("RegisterService","Cannot create a new app to register")
+            val message = "Cannot create a new app to register"
+            Log.w("RegisterService", message)
+            sendRegistrationFailed(context!!,application,connector_token,message)
             return
         }
         db.registerApp(application, app.id, app.token, connector_token)
@@ -86,13 +90,13 @@ class RegisterBroadcastReceiver: BroadcastReceiver() {
     override fun onReceive(context: Context?, intent: Intent?) {
         settings = Settings(context)
         when (intent!!.action) {
-            REGISTER ->{
+            ACTION_REGISTER ->{
                 val db = MessagingDatabase(context!!)
                 Log.i("Register","REGISTER")
-                val internalToken = intent.getStringExtra("token")?: ""
-                val application = intent.getStringExtra("application")?: ""
+                val internalToken = intent.getStringExtra(EXTRA_TOKEN)?: ""
+                val application = intent.getStringExtra(EXTRA_APPLICATION)?: ""
                 thread(start = true) {
-                    registerApp(db, application, internalToken)
+                    registerApp(context, db, application, internalToken)
                     Log.i("RegisterService","Registration is finished")
                 }.join()
                 val token = db.getGotifyToken(application, false)
@@ -101,10 +105,10 @@ class RegisterBroadcastReceiver: BroadcastReceiver() {
                 sendEndpoint(context,application,endpoint)
                 db.close()
             }
-            UNREGISTER ->{
+            ACTION_UNREGISTER ->{
                 Log.i("Register","UNREGISTER")
-                val token = intent.getStringExtra("token")?: ""
-                val application = intent.getStringExtra("application")?: ""
+                val token = intent.getStringExtra(EXTRA_TOKEN)?: ""
+                val application = intent.getStringExtra(EXTRA_APPLICATION)?: ""
                 thread(start = true) {
                     val db = MessagingDatabase(context!!)
                     unregisterApp(db,application, token)