MQTT publish fails

I’m currently trying out mosquitto and wanted to test it using postman. Connecting works fine, subscribing works fine, but when I tried to publish, I got this error.

Unable to publish message: Cannot read properties of undefined (reading ‘toString’)

Hi @joint-operations-te8, thanks for reaching out! Could you share a bit more information to help us try to find the issue?

  • What version of Postman are you using? Which OS are you on?
  • Are you running mosquitto locally or using an online test broker?
  • Can you provide an example of what kind of message you’re trying to publish?

Hi Jonathan,

I’m currently using v11.1.14 of Postman on Windows 10.
I’m hosting mosquitto on a “cloud” server that we have.
I was just going to send a plain text and it was already failing. Then I tried something that looks like a JSON string, and it also failed.

Are you trying to send any properties along when you publish? I’m having a bit of an issue trying to reproduce the issue on my end. Could you share a version of the request you’re trying to send?

Do you see the same issues when trying to publish to “”?

Hi, I was just sending some random text with and without a double quote. I’m not sending any property as I don’t know how to do that. Also, I was triggering a publish using the mosquitto cli straight from the server, so I guess that made it “effortless” for that step, but not the other way around. I also made mosquitto allow anonymous connections for easy testing. This is the tutorial I followed to do the initial setup of mosquitto. Installing Mosquitto broker on Debian | by Ross Anderson | Medium