title: Firebase FCM push, getting Error Missing Registration | Android
body: <p>I have seen this topic discussed before, but I think it's not the same scenario.</p>
  
  <p>I'm trying to send push notification from one device (going to be an admin device) through FCM (Firebase Cloud Messaging) to all other devices, and i'm going exactly by their docs.</p>
  
  <p>I have tried to subscribe to topics or keep it simple still getting the same <strong>error</strong>: </p>
  
  <blockquote>
    <p>MissingRegistration</p>
  </blockquote>
  
  <pre><code> String jsonData = "{\"to\":\"/topics/news\",\"notification\":{\"title\":\"title\",\"body\":\"text\" }}";
                  byte[] postData = jsonData.getBytes(Charset.forName("UTF-8"));
                  int postDataLength = postData.length;
  
                  URL url = new URL("https://fcm.googleapis.com/fcm/send");
                  HttpURLConnection con = (HttpURLConnection) url.openConnection();
                  con.setDoInput(true);
                  con.setDoOutput(true);
                  con.setInstanceFollowRedirects(true);
                  con.setRequestMethod("POST");
  
                  con.setRequestProperty("Content-Type","application/json");
                  con.setRequestProperty("Authorization","key=AIzaSyB70J***-z34q2_h*******qjZsM5zBIf8Y"); //I've added stars :-) 
                  con.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
                  con.setRequestProperty("Content-Type","charset=UTF-8");
                  con.setRequestProperty("Content-Length",Integer.toString(postDataLength));
  
                  con.setUseCaches(false);
  
                  DataOutputStream wr = new DataOutputStream(con.getOutputStream());
                  wr.write(postData);
  
                  InputStream inputStream= con.getInputStream();
                  BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                  String line = null;
                  String outPut = "";
                  while (((line = reader.readLine()) != null)){
                      outPut += line;
                  }
  </code></pre>