Comments on: Raspberry Pi Pico W: Getting Started with MQTT (MicroPython)

By: Peter Merchant

Peter Merchant — Wed, 15 Apr 2026 12:42:38 +0000

In reply to Emilio. I can't find it. 15 April 2026

By: Peter Merchant

Peter Merchant — Wed, 15 Apr 2026 11:23:04 +0000

In reply to Gary. This is where I am. I created a MQTT publisher on a WEMOS D1 communicating to a Raspberry Pi with Mosquito, and the subscriber program. This was programmed in Arduino language. Now I want to convert my Publisher device to a PICO using MicroPython. It looks like a config file is needed on the PICO and then my Publisher file. I'll see how it goes using this tutorial.

By: Sara Santos

Sara Santos — Wed, 18 Feb 2026 11:10:56 +0000

In reply to Luc Coussement.

The client ID identifies the client.
That is just needed in the Pico code.
Regards,
Sara

By: Luc Coussement

Luc Coussement — Tue, 17 Feb 2026 15:54:44 +0000

Hi
the mosquitto works also.
the user and password must have high comma.
example:
mosquitto_pub -h xxxxx.cloud -p 8883 -t pico/led -m “OFF” -u ‘xxx’ -P ‘yyy’ -d
^ ^ ^ ^
but no Cliend id

wat is de function of the cliend id?

Thanks. for help!

Regards,
Luc

By: Luc Coussement

Luc Coussement — Tue, 17 Feb 2026 15:14:40 +0000

In reply to Sara Santos.

Hi
Thanks.

2 pico’s is now working.
but node-red no connection with Client ID

By: Sara Santos

Sara Santos — Tue, 17 Feb 2026 11:25:14 +0000

In reply to Luc Coussement.

Ok.
Thanks.

If you want to connect a second RPi Pico, you need to set a different MQTT Client ID.

MQTT_CLIENT_ID = b’raspberrypi_picow’

Regards,
Sara

By: Luc Coussement

Luc Coussement — Tue, 17 Feb 2026 08:31:16 +0000

In reply to Luc Coussement.

Hi,

This is only about how to establish the connection to the Cloud Broker HiveMQ.
If, after creating an account, the connection using the provided URL and port number does not work everywhere (for example with one Pico and without Node-RED),

it is better to use the URL “broker.hivemq.com” and port “1883”.

I just want to share my findings and solution with you.
Please review and test whether this is worth mentioning, as it could improve the article.

Kind regards,
Luc

By: Luc Coussement

Luc Coussement — Mon, 16 Feb 2026 18:37:26 +0000

Hi
I am working with de Cloud Broker HiveMQ
Regards
Luc

By: Sara Santos

Sara Santos — Mon, 16 Feb 2026 16:45:24 +0000

In reply to Luc Coussement.

Hi.
It should work with Node-RED and Raspberry Pi with the Mosquitto broker if that’s your question.
I tested it very recently.

You need to be more specific when you say it doesn’t work, otherwise it’s very difficult to figure out what might be the problem.

Regards,
Sara

By: Luc Coussement

Luc Coussement — Mon, 16 Feb 2026 10:25:33 +0000

This was a good explanation about MQTT.
It works perfectly.

But when I use a second Pico to control the on/off function, I get an error: Error -1 in mqtt_subscribe.py.

It doesn’t work with Node-RED (no connection).
It also doesn’t work with the Raspberry Pi.

After some searching, I found that it is better to use the URL “broker.hivemq.com” and port “1883”,
and not the registration URL.

Example:
Raspberry Pi:
mosquitto_pub -h broker.hivemq.com -p 1883 -t pico/led -m "ON" -u xxx -P yyy

Node-RED also works this way.

There is one disadvantage you cannot use the HiveMQ web page to view the subscribed topics.

Could you please look into this?

Kind regards,
Luc