This is the flow (cut down) [{"id":"54dcbdbf.2fe7a4","type":"inject","z":"c56bddee.ca0a18","name":"test","topic":"","payload":"","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":520,"y":1810,"wires":[["37f3cedd.fe71da"]]},{"id":"37f3cedd.fe71da","type":"function","z":"c…

You have set msg.payload to a String. A string property in JavaScript cannot have properties of its own. That is why msg.payload.wap doesn't get set. If you want to send multiple values in the one payload then you need to set payload to be an object: msg.payload = { payload: msg.payload + " CH…

read the Info panels for both the MQTT in and out nodes... What do they say the node accepts as inputs and provides as outputs ?

dceejay. Yes, I believe I have. The other (recent) problem should have been suffice for me to work out what I need to do. In that it is Arduino code. This is Node.Red (JavaScript). So the msg.payload is the carrier. So I tried setting msg.payload.wap as shown in the first function node. msg.…

Jay, Ok, looked. This is what I now have in the second function node: msg.payload = msg.payload + " CHANGED "; node.warn(msg.payload); node.warn(msg.wap); node.warn(msg.payload.wap); JSON.parse(msg.payload); return msg; I get the first warning, the second. Third undefined and there is no furt…

Put a debug node showing the complete message showing the input to that function node and see what it shows. [Edit] and show us what you see for the node.warn messages.

This is what I see: There are three node.warn() outputs. (blue lines) There is the message being sent INTO MQTT (red line) [Screenshot%20from%202019-06-08%2017-52-01] Then you see the MQTT output (red lines) and the missing msg.wap (yellow bits) [Screenshot%20from%202019-06-08%2017-52-08]

Thank you Nick. I forgot the msg.payload.payload trick. I hope next time I do remember.

MQTT, message formats (again) stuck

General

JayDickson 8 June 2019 02:39 3

You may have some luck with the functions I use in this post. I find them very useful in communicating between multiple instances of node-RED, but there are lots of other uses too.

Topic		Replies	Views
MQTT - what used to work now doesn't. Or so it seems. Structure of messages General	10	609	22 May 2020
MQTT, payload, JSON and wanting to check General	7	335	27 February 2023
JSON{} node question General	1	403	24 July 2018
MQTT is driving me crazy. How to format messages - again, sorry General	16	253	12 January 2023
Handling many JSON msg payload General mqtt	10	377	14 March 2023

MQTT, message formats (again) stuck

Related topics