public function validatePort($port = null)
    {
        if ($port === null) {
            $port = $this->_port;
        }

        // If the port is empty, then it is considered valid
        if (strlen($port) === 0) {
            return true;
        }

        // Check the port against the allowed values
        return ctype_digit((string) $port) and 1 <= $port and $port <= 65535;
    }