Everlasting log entry in Mosquitto Broker

In my logfile of the Mosquitto-Broke I have thousands of entries like this

New connection from 172.30.32.2 on port 1883.
Socket error on client <unknown>, disconnecting.

What hides behind this URL and how can I block this?

If I remember it correct, it’s supervisor checking, if Mosquitto is alive and you can ignore this.