question

kannst du die Frage im deutschen Bereich noch mal stellen ? Verstehe nicht was du da machen willst.

I use a (very) simple function node which is triggered every 20 seconds (could be a little longer).

msg.topic = 'R/cxxxxxxxxx4/keepalive'
msg.payload = ''
return msg;

Thank you Gerard!

What format is the data you send? String, JSON, ...?

How to get the return msg in Node-Red done?

Dear Joe,

this is my very first answer in this forum. So don`t be too harsh to me;-)

All information about the keep-alive of the mqtt broker of the victronOS you'll find at: https://github.com/victronenergy/dbus-mqtt.

I send the keep-alive within a Node-RED flow (attached at the end of my answer).

XXXXXXXXXXX

needs to be adopted to your venusOS installation. As well as the broker address:

"broker": "XXX.XXX.XXX.XXX",

which corresponds to the ip-address of your venusOS. BTW in my case it is a venusOS on a Raspberry PI.

The main difference with the suggested:

  
                  

                   
msg.topic = 'R/cxxxxxxxxx4/keepalive'
                   
msg.payload = ''
                   
return msg;
                  

is:

I only "request" the topics I am interested in. If you send only an empty string as payload you'll get ALL topics send.

The payload needs to be a json list as listed below:

"payload": "[\"system/0/Dc/Battery/#\",\"system/0/Ac/Consumption/#\",\"system/0/Timers/#\",\"battery/1/#\",\"solarcharger/#\"]"

The topics I am interested in I checked manually with the complete topic-list:

(I personally do NOT use Microsoft products... so this is done on an xterm)

mosquitto_pub -h XXX.XXX.XXX.XXX -m '' -t 'R/XXXXXXXXXXX/keepalive
mosquitto_sub -v -I myclient_ -t "#" -h XXX.XXX.XXX.XXX > all.txt

In all.txt ALL topics are collected.

Some screenshots:

The flow.

The list of topics.

Interval set to 50 seconds.

I hope for someone is this post usefull...

Best regards

Marc

[
    {
        "id": "11e7538c7954de75",
        "type": "tab",
        "label": "keepAlive",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "9f8ba7eb9957abd1",
        "type": "inject",
        "z": "11e7538c7954de75",
        "name": "keepAlive",
        "props": [
            {
                "p": "payload"
            }
        ],
        "repeat": "50",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "payload": "[\"system/0/Dc/Battery/#\",\"system/0/Ac/Consumption/#\",\"system/0/Timers/#\",\"battery/1/#\",\"solarcharger/#\"]",
        "payloadType": "json",
        "x": 230,
        "y": 160,
        "wires": [
            [
                "34c4a2c6e0eeda47",
                "c234e95aac810b09"
            ]
        ]
    },
    {
        "id": "34c4a2c6e0eeda47",
        "type": "mqtt out",
        "z": "11e7538c7954de75",
        "name": "",
        "topic": "R/XXXXXXXXXXX/keepalive",
        "qos": "2",
        "retain": "",
        "respTopic": "",
        "contentType": "",
        "userProps": "",
        "correl": "",
        "expiry": "",
        "broker": "0aa70d5af5427c60",
        "x": 660,
        "y": 160,
        "wires": []
    },
    {
        "id": "c234e95aac810b09",
        "type": "debug",
        "z": "11e7538c7954de75",
        "name": "debug 2",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "false",
        "statusVal": "",
        "statusType": "auto",
        "x": 600,
        "y": 240,
        "wires": []
    },
    {
        "id": "0aa70d5af5427c60",
        "type": "mqtt-broker",
        "name": "VenusOSmqtt",
        "broker": "XXX.XXX.XXX.XXX",
        "port": "1883",
        "clientid": "",
        "autoConnect": true,
        "usetls": false,
        "protocolVersion": "4",
        "keepalive": "60",
        "cleansession": true,
        "birthTopic": "",
        "birthQos": "0",
        "birthPayload": "",
        "birthMsg": {},
        "closeTopic": "",
        "closeQos": "0",
        "closePayload": "",
        "closeMsg": {},
        "willTopic": "",
        "willQos": "0",
        "willPayload": "",
        "willMsg": {},
        "userProps": "",
        "sessionExpiry": ""
    }
]