code: public String[] getRegisteredListeners(RESTRequest request,
                                             int clientID,
                                             String source_objName) {
          //Get the client area
          ClientNotificationArea clientArea = getInboxIfAvailable(clientID, null);
  
          List<ServerNotification> registrations = clientArea.getServerRegistrations(request, source_objName);
  
          if (registrations != null) {
              List<String> listeners = new ArrayList<String>();
  
              //loop registrations to match request
              for (ServerNotification registration : registrations) {
                  listeners.add(registration.listener.getCanonicalName());
              }
  
              return listeners.toArray(new String[listeners.size()]);
          }
  
          return null;
      }
docs: Returns an array of listener ObjectNames (as strings) that are listening for server-side notification from the
  given source mbean.