MQTT bad formatted packet (IFM MasterIOLink)

Hello everyone,

I’m trying to get data from an IFM Master IO Link (AL1322).
The connection works great.

CirrusClient 16May2023 11:38:13 ME-4aacfd3a-8014-42a5: MQTT Client connected to tcp:// on thread Thread-60054
CirrusClient 16May2023 11:38:12 ME-4aacfd3a-8014-42a5: Connected to tcp://
CirrusClient 16May2023 11:38:12 ME-4aacfd3a-8014-42a5: connect with retry succeeded

But I can’t manage to know why I keep having this warning and I can’t get my data.
NettyMQTTHandler 16May2023 11:39:14 Error decoding a packet, probably a bad formatted packet, message: Invalid protoName: MQTT

My Master configuration :

If one of you already did this, I would love some help.

Thank you very much.

What MQTT Server are you using? Is it MQTT Distributor?

yes, I’m using MQTT Distributor.

We already have devices (PLC) using MQTT, and it works.

I created a custom Namespaces in MQTT Engine with “MasterIFM/#” subscriptions.

Can you try upgrading to the latest MQTT Distributor version? We should be able to debug this a bit better if you do. The message you are seeing indicated the MQTT CONNECT packet from your device is malformed. What’s add is that it is complaining the protocol type is wrong. But, ‘MQTT’ is valid for a MQTT 3.1.1 connection. Can you connect this device to any other MQTT Servers?


I updated the MQTT modules (now : 4.0.15), and this is now the messages I get.

I will try to connect the device to another MQTT server.

thanks for you help