I would like to split this thread in 2 pieces, if you agree:
1. Check, so that we are sure that all the tools are functioning.
2. Try to communicate with APSystems
You said
You said also
I wonder, how did you check that?
As you have installed Node Red and Mosquitto (MQTT) you should now be able to open the Node Red workflow editor in any browser
Point your browser to: http://<ip_address of node red>:1880.
Now you should see see the workbench in the middle, at the left the library, with all installed nodes and at the right the info/debug pane,
Now it is time to play a little with node red, in order to get acquainted with this tool.
A good starting point is: https://nodered.org/docs/
Also http://noderedguide.com/ may help you a lot.
With
I mean that you should make your first small flow.
As follows:
1. Drag and drop the MQTT in Node on the workbench
Configure this node as follows:
Double Click on the node in the workbench
You may give the server a name, e.g. MQTT broker
Enter your topic, you want to subscribe to. In this case domoticz/out
Leave the output as auto-detect
QoS you can leave
Name is optional and up to you to decide
Click on the pencil at the right side of the server name
At Connection you fill in the IP address of the broker and the port stays default (1883).
Tick also the checkbox, called "Use legacy MQTT 3.1 support"
If you have secured your broker (as advised) with a username/password fill in the fields in the "Security" Tab
The rest you can leave for this moment.
Deploy (the red button in the right top corner)
If you did everything correct you will see below the MQTT node a green dot with connected.
2. The next thing we do is that we drag and drop from the output section the debug node.
You may double click on it and give it a name but that is optional
3. Draw a line from the output of the MQTT In node to the debug node, so that you have the following flow:
Do not forget to press Deploy
3. If you go now to the debug pane
Press Ctrl+ g and the d or click on the debug symbol, right beside info.
If everything is succesfull you will see debug output from domoticz.
If you can see output from Domoticz you have checked that both Domoticz and Node Red can communicate with your broker.
But you have verified already a couple of things, so maybe you find it already yourself.
I come back to AP Systems issue later.
Regards