protected function disconnect()
    {
        $this->log('-- disconnecting' . PHP_EOL, self::VERBOSITY_ALL);

        fflush($this->stdout);
        fclose($this->stdout);
        fclose($this->stdin);

        $this->stdin  = null;
        $this->stdout = null;

        $this->log('-- disconnected' . PHP_EOL, self::VERBOSITY_ALL);

        if (is_resource($this->logFile)) {
            fflush($this->logFile);
            fclose($this->logFile);
            $this->logFile = null;
        }

        return $this;
    }