public function readIPAddress()
    {
        if (!is_resource($this->fp)) {
            return $this->raiseError('not connected');
        }

        $buf = @fread($this->fp, 4);

        return sprintf('%d.%d.%d.%d', ord($buf[0]), ord($buf[1]),
            ord($buf[2]), ord($buf[3]));
    }