I have MQTT explorer installed and running. I am getting 3 message being published every..... so often, that are no longer needed. Their TOPICs are STATUS/(device name) They aren't retained and if I delete them, they come back fairly quickly. I can't find a node (MQTT OUT) with that in the topic field. So the device name is set before it gets to the node. (And probably the whole topic.) Yes, not really Node-red's problem. I'm just looking for help to find who is sending the messages. Update: This is a screen shot - just to show you. [Screenshot from 2023-10-03 13-55-34] (red areas) So I have 3 messages. Topics: STATUS/BedPi, STATUS/TelePi and STATUS/TimePi The value changes - up and down - with each message. So, thought 1: STATUS/BedPi shouldn't be hard to find if I search for it in a MQTT OUT node. All 3 machines searched. NOTHING! Ok, not to be outdone: Search for STATUS in MQTT OUT nodes and back track from there. Nothing exciting there either. I guess last option is to search for all topic empty MQTT OUT nodes and back track from them.

How many search hits do you get for "myDevicename"? Presumably one hit is where msg.topic is constructed for mqtt, either a function or a change node.

Thanks. That's good to know. Honestly though I guess it was me who didn't name the topic as well a I should. But I guess that is all part of actually learning. I've re-written/structured a fairly big part of the working of my 3 main machines and their comms of what is going on with things. Probably about 1 full day of man hours work. And ITMT a fairly serious bit of Arduino programming done on another project. Structures crossed up and mistaken between the languages. How easy is it to install? (Just since we are here)

[image] Trying_to_learn: How easy is it to install? you already have MQTT v5. Just select the option on the broker config node. (assuming you are using a recent enough broker like Mosquitto v2+ which supports V5)

No, 3.11 :frowning: Ah, Ok, select Version 5 in the drop down. Thanks.

@Steve-Mcl without straying too far off topic... should users be generally using v5 by default now, even if they are not using its advanced features? ...and how does v5 affect external devices, such as Shellie's, etc.

[image] Paul-Reed: should users be generally using v5 by default now It has other benefits like richer error reporting (so when something goes skewwhiff there is a chance you know why). Also, when you sub to multiple same topic, you dont start getting mutiple subs where you expected 1. It is also faster in cases where topic aliases are used. However, I dont think 3.11 is going anywhere just yet. [image] Paul-Reed: ...and how does v5 affect external devices, such as Shellie's, etc. Most (if not all) brokers that support v5, also supports 3.11, so if the shellies only support 3.11, they can still play alongside your v5 connected Node-REDs

[image] Steve-Mcl: If someone REALLY did need to add traceability to your publishers, then MQTT V5 can help here. I really must update all of my flows to use this! Though sadly, MQTT Explorer has never been updated to work with MQTT v5 so it would be hard to easily see the extra data. Previously, I've always got round this issue by making sure that the output topic also has sub-topics that say where and when the topic update came from. [image]

[image] TotallyInformation: Though sadly, MQTT Explorer has never been updated to work with MQTT v5 so it would be hard to easily see the extra data. I still use MQTT explorer but my other go-to is improving lots (has MQTT v5 as well): https://mqttx.app/features

Yes, I've just tried that. But it has a major flaw - it does not show a topic hierarchy like Explorer does which is a pain if you are trying to oversea your whole broker - this is what Explorer excels at. So you can't really monitor anything that has a high volume of updates very easily. Looks like I need to revisit some ideas I had previously about creating something in Node-RED. :slight_smile:

[image] TotallyInformation: Looks like I need to revisit some ideas I had previously about creating something in Node-RED. :slight_smile: That would be useful :+1:

No visualisation yet but something to grab whole topic hierarchies - put this into a function node: // Just a safety measure to prevent too much recursion // Change if you have crazy deep topic hierarchies const maxLevels = 9 function doTopic(topicsPart, keys, level = 0) { if (level > maxLevels) return // no infinite loops! let key if (Array.isArray(keys) && keys.length > 1) { // Grab the top level key (make sure it is a string) // MQTT topic parts could be number - don't want an accidental array key = `${keys.shift()}` // Make sure that the property exists as the next level if (!topicsPart[key]) topicsPart[key] = { _count: 1 } else topicsPart[key]._count++ // Recurse to the next level doTopic(topicsPart[key], keys, level++) } else { // Must be at the end of the topic chain if (!Array.isArray) keys = [keys] // make sure it is an array // MQTT topic parts could be number key = `${keys[0]}` // make sure it is a string if (!topicsPart[key]) topicsPart[key] = { _count: 0 } topicsPart[key]._count++ topicsPart[key]._value = msg.payload topicsPart[key]._userProperties = msg.userProperties } } const topics = flow.get('mqtt') ?? {} const splitTopic = msg.topic.split('/') doTopic(topics, splitTopic) // flow.set('mqttTopics', topics) flow.set('mqtt', topics) // Don't do this with bazilions of topics! return msg

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How can I find out who is publishing a message in MQTT?

General

TotallyInformation 6 October 2023 11:12 31

The other thread:

Topic		Replies	Views
Features provided by mqtt and node-red General	4	949	4 May 2022
MQTT devices being reset fairly frequently General	3	360	6 June 2021
Why cant I see any MQTT messages on debug node General	9	326	7 December 2023
Stuck with what's happening with MQTT topics General	12	505	21 November 2025
MQTT Dynamic topic and publish the messages General	3	1089	25 October 2021

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How can I find out *who* is publishing a message in MQTT?

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How can I find out who is publishing a message in MQTT?