MQTT activation failed. The MQTT connection was made by Server rejected. Error code: 88

[Dominik_B]

I installed the ioBroker on my Raspberry Pi 5. Using the MQTT Server Adapter, I want to communicate with my Nuki Smart Lock 4 Pro using MQTT.
Port is set to 1883, as Nuki wants it to be.

However, my IP address from MQTT Server is 192.162.1.9.

This IP address probably does not fit the Nuki and therefore I get the following error message:

MQTT activation
failed.

The MQTT connection was made by
Server rejected. Please check your
Configuration.

Error code: 88

Since I have independently trained over 70 devices in the WLAN to my IP address range, I do not want to use any other address range.

What can I do now?

A similar topic with no useful solution is available here:

Error code 88 trying to configure a Home Assistant MQTT server

Why is there this limitation? Are there security implications I should be aware of if I alias one of my server IPs or is it simply a decision to follow the standard? After configuring an alias on my router everything seems to be working fine.

Greetings Dominik

[Juergen (Jürgen Pansy)]

@Dominik_B

my IP address from MQTT Server is 192.162.1.9.

This is not a private IP range, but a public one and therefore not allowed (see MQTT spec).

Depending on what your infrastructure supports, you could try to add multiple IPs to your MQTT server or router (and use port forwarding to forward data to the MQTT server).