public function setProtocolLevel($value)
    {
        if ($value < 3 || $value > 4) {
            throw new \InvalidArgumentException(sprintf('Unknown protocol level %d.', $value));
        }

        $this->protocolLevel = $value;
        if ($this->protocolLevel === 3) {
            $this->protocolName = 'MQIsdp';
        } elseif ($this->protocolLevel === 4) {
            $this->protocolName = 'MQTT';
        }
    }