code: public String[] getRegisteredIDs(RESTRequest request,
                                       int clientID,
                                       String source_objName,
                                       String listener_objName) {
          //Get the client area
          ClientNotificationArea clientArea = getInboxIfAvailable(clientID, null);
  
          List<ServerNotification> registrations = clientArea.getServerRegistrations(request, source_objName);
  
          if (registrations != null) {
              List<String> ids = new ArrayList<String>();
  
              //loop registrations to match request
              for (ServerNotification registration : registrations) {
                  if (registration.listener.getCanonicalName().equals(listener_objName)) {
                      //found a matching registration, so add ID to list
                      ids.add(registration.filter + "_" + registration.handback);
                  }
              }
  
              return ids.toArray(new String[ids.size()]);
          }
  
          return null;
      }
docs: Return an array of IDs (strings) that represent server-side notifications from the given source mbean to the given listener mbean.