MQTT is a perfect lightweight protocol for managing home electronic devices. The only thing that is not very convenient is the need to know the IP of the MQTT broker for all MQTT clients. Meanwhile this IP may well change in a home router (being a router will be replaced, in case of a failure with a router, or if a home NET's topology will be changed), or in case of the replacing a MQTT computer with a new one.

It’s not very difficult to change the IP of the MQTT broker within MQTT clients codes (talking about DIY devices), but if this device was deployed a long time ago, it’s not so easy to recall all program code for making changes and restore all programming toolchains.

Described the MQTT-driven IP-relay module, on which the variable part of the MQTT broker’ IP address is set by mechanical switches, and in case of changing this address it is not necessary to change the program of the relay module.