Advice on how to debug MQTT connection problem

[Andrew Fiddian-Green]

I am having a problem with a Tasmotized Sonoff not connecting to the MQTT broker, and would appreciate advice how to debug this.

The MQTT broker is Mosquitto running on a Raspberry Pi; I can successfully connect to it from various MQTT clients such as MQTT.fx, MQTT Explorer, and can subscribe and publish to it. I also have OpenHAB client Things connected to it, and they can also publish and subscribe. (So in other words, I have one MQTT broker and four different clients all singing from the same song book).

But then I also have a Tasmotized Sonoff TH16 which does NOT connect to the MQTT broker (see console log below).

16:44:43 MQT: Attempting connection...
16:44:47 MQT: Connect failed to 191.168.1.131:1883, rc -2. Retry in 10 sec

All clients (including the Sonoff) are set up identically as follows..

Host: 191.168.1.131 // NOTE: IP address rather than Host Name to avoid DNS issues

Port: 1883

User: myName

Pwd:  myPassword

The Sonoff is physically connected via 2.4GHz wi-fi, and the other clients are on Ethernet. All clients are on the same IP sub-net, and all clients received their IP addresses via DHCP (auto) from the same router. I can connect to the Sonoff via HTTP on its web server, so there is active routing between the Ethernet and Wi-Fi parts of the LAN (I even connected Wireshark and can see this traffic). The router is a Ubiquiti EdgeMax EdgeRouter Lite, and the Wi-Fi is via Ubiquiti UNIFI wireless access points.

I know that "rc -2" means "failed to connect". But why??

[Andrew Fiddian-Green]

SOLVED: I was trying to connect to a wrong IP address 191.xx instead of 192.xx -- Doh!

[Lester Bennett]

Isn't it amazing how you can keep looking at something like that and not see the mistake.

The mind sees what it expects to see.

[Greg from Oz]

And that's why you copy and paste from a working example......been there done that.

Good it's working.