public function isConnected()
    {
        try {
            return \is_resource($this->connection) && \ftp_rawlist($this->connection, $this->getRoot()) !== false;
        } catch (\ErrorException $e) {
            if (\strpos($e->getMessage(), 'ftp_rawlist') === false) {
                throw $e;
            }

            return false;
        }
    }