Home Assistant Community — Smart Home — Sat, 29 Aug 2026 16:43:07 +0000
Summary
A user who previously installed Z2MQTT and the MQTT app with default settings reported that the setup works fine with their Zigbee devices. While exploring how to connect Fully Kiosk tablets to MQTT to use their cameras as motion detectors, they discovered an error message repeating every five seconds in the MQTT logs. The log shows a connection from address fd0c:ac1e:2100::1:43288 on port 1883 failing with "received null username or password for unpwd check," followed by client "c6ed1456" being disconnected as "not authorised." The user is asking how to identify which device on their network is generating these repeated unauthorized connection attempts.
Some months ago I installed Z2MQTT and the MQTT app, with no special configuration (defaults all the way). And it works fine with a whole load of zigbee devices.
I’m now looking into how to get a couple of Fully Kiosk tablets onto MQTT so I can use their cameras as motion detectors, and it turns out I haven’t the faintest idea how to do that - but that’s a different topic. While poking around, I looked at the MQTT logs and found the following error message coming up every 5 seconds.
2026-08-29 17:30:56: New connection from fd0c:ac1e:2100::1:43288 on port 1883. error: received null username or password for unpwd check 2026-08-29 17:30:56: Client c6ed1456 [fd0c:ac1e:2100::1:43288] disconnected: not authorised.
How do I find out what device is being referred to?
Original article: https://community.home-assistant.io/t/mqtt-recurring-error-message/1023142 Source: Home Assistant Community