MQTT over Websockets

General
1

Hello all,

I try to retrieve data from the Notification service of the Royal Netherlands Meteorological Institute (KNMI), but I do not have any experience with MQTT over Websockets and so this is quite new for me.

Perhaps someone with more experience sees it immediately and can give a hint.

The server has the following configuration (see: Notification Service)

Screenshot_KNMI_Notification

My "MQTT Input" node has the following configuration:

Screenshot_MQTT Input_KNMI
Screenshot_MQTT Input_KNMI574Ă—546 24.3 KB

and

Screenshot_MQTT Input_Config_KNMI
Screenshot_MQTT Input_Config_KNMI654Ă—660 30.9 KB

I tried several different settings in the configuration, but the node does not connect and keeps showing "connecting".

I also tried it with MQTT Explorer, but that does not connect either.
I'm able to "ping" the server, so the server is online.
A simple https://mqtt.dataplatform.knmi.nl/ gives a message "Not found".

Has anybody an idea?

Thanks in advance,

Regards and Merry Christmas.

2

Try removing the :443 from the host name and set the port entry to 443

3

Thank you, Steve, for your quick response.

Your suggestion to remove :443 after the host name and enter it in the port field does not work.
As soon as you put :// in front of the host name, such as ws:// or wss:// the port entry field is disabled (greyed-out)

I got the suggestion from:MQTT over WebSocket - Datacake Docs and also from: Accessing MQTT Broker using websockets from Node-RED – Cymplecy (Simplesi)

I also checked https://groups.google.com/g/node-red/c/ByzqoQdkGMI, where Nick said, in fact, the MQTT over Websocket does not exist in Node-RED. This is approx 6 years ago and the time might have been changed since then. However I never saw the PR from Jacobo del Bosque.

Any other suggestions?

Regards

1 Like
4

It does work (I'm certain :thinking:) but I'm not in a position to try it out to show you. Will be home later. Hopefully someone will pop by with a quick how to before then.

Note: you will need to send me (private message (click my avatar->message)) with details of your MQTT server if you want me to try for you.

5

Are you able to try out the python example to see if that works?

6

Hello@Steve-Mcl

I will send you the broker details in a PM.
[Edit: Done]

Hello @cymplecy

Simon, thank you for jumping in.

I think, you mean the python example at Notification Service.

After a small modification of the script and inserting the CLIENT_ID and the TOKEN I got a positive result. I had to add the shebang (#!/usr/bin/python3)
The result:

pi@RPi1:~ $ ./KNMI-test.py 
INFO:__main__:Connected using client ID: b'42117fea-e6dc-49e8-b976-62c8a8586705'
INFO:__main__:Session present: 1
INFO:__main__:Connection result: Success
INFO:__main__:Subscribed to topic 'dataplatform/file/v1/radar_echotopheight_5min/1.0/#'
INFO:__main__:Received message on topic dataplatform/file/v1/radar_echotopheight_5min/1.0/created: b'{"specversion": "1.0", "type": "nl.knmi.dataplatform.file.created.v1", "source": "https://dataplatform.knmi.nl", "id": "440c1390-c56b-0d18-5c39-197d856f88c2", "time": "2023-12-24T17:30:34Z", "datacontenttype": "application/json", "data": {"datasetName": "radar_echotopheight_5min", "datasetVersion": "1.0", "filename": "RAD_NL25_ETH_NA_202312241725.h5", "url": "https://api.dataplatform.knmi.nl/open-data/v1/datasets/radar_echotopheight_5min/versions/1.0/files/RAD_NL25_ETH_NA_202312241725.h5/url"}}'
INFO:__main__:Received message on topic dataplatform/file/v1/radar_echotopheight_5min/1.0/created: b'{"specversion": "1.0", "type": "nl.knmi.dataplatform.file.created.v1", "source": "https://dataplatform.knmi.nl", "id": "f9390589-8c8b-01aa-293f-f741c1c3f870", "time": "2023-12-24T17:35:33Z", "datacontenttype": "application/json", "data": {"datasetName": "radar_echotopheight_5min", "datasetVersion": "1.0", "filename": "RAD_NL25_ETH_NA_202312241730.h5", "url": "https://api.dataplatform.knmi.nl/open-data/v1/datasets/radar_echotopheight_5min/versions/1.0/files/RAD_NL25_ETH_NA_202312241730.h5/url"}}'

So every 5 minutes I receive a message from the Python script. My conclusion so far is that the endpoint is giving a valid response.

I hope this is enough information for you.

Thanks for your time to look into this issue.

Regards

1 Like
7

Great that you got that working - it verifies that your API key and all the other information is correct :slight_smile:

8

I think it defaults to 1883 if the port is not set, and the port cannot be set when using ws(s)://

9

Yes, as soon as you insert :// in front of the hostname, such as ws:// or wss:// the port field is disabled. Therefore I found the suggestion to add the port after the hostname.

See links above.

However playing with this gives not any results and it ends even in a crash of Node-RED.

Regards

10

If you need a temporary work around, you could set up a local broker. Talk to that over mqtt. Then get it to talk to the remote broker over websockets.

11

I have certainly had this working, though I don't have a working wss server at the moment. Looking at the server node setup I see that I entered the the port number in the same way you have, but it also shows as greyed out in the port field. I assume that I entered that field before filling in the url. That should not make a difference but you never know.

Can you show us the crash please? In fact start node red in a command window and show us the full node red startup output up to the crash.

12

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