public function update($itemName, $eventsMap, $isSnapshot)
 {
     $requestId = $this->getActiveItem($itemName);
     if (!is_null($requestId)) {
         $snapshotFlag = RemoteProtocol::encodeBoolean($isSnapshot);
         $qry = "UD3|S|{$itemName}|S|{$requestId}|B|{$snapshotFlag}";
         foreach ($eventsMap as $field_name => $field_value) {
             $enc_field_name = RemoteProtocol::encodeString($field_name);
             $enc_field_value = RemoteProtocol::encodeString($field_value);
             $qry .= "|S|{$enc_field_name}|S|{$enc_field_value}";
         }
         $this->doNotify($qry);
     } else {
         echo "Unexpected update for item [{$itemName}]!\n";
     }
 }