Internet of Things systems are widely used today and they are constantly increasing. Since these systems use IoT devices that are powered by some source of electricity (batteries, solar cells, etc.), the aim is to keep this consumption to a minimum so the system can operate independently for as long as possible. That is why communication protocols such as Bluetooth Low Energy and MQTT were designed and implementation of which is explained and demonstrated in this work. The concept of the Internet of Things also includes devices that retrieve data and communicate with each other and servers that collect data and later manipulate it. The ESP32 microcontroller is a simple IoT device that has BLE technology supported and provides easy programming via the Arduino IDE, so it has been used in this work. The server that was also used in the work is MQTT Broker, which is located on the IoT platform Home Assistant, built on a virtual machine. The Home Assistant platform provides much greater capabilities than shown in the paper, but due to the requirements of the Internet of Things demonstration system, it is only used as an MQTT server with the ability to display incoming MQTT messages. On the whole, the IoT system used in the paper mimics a system that would retrieve temperature data from the end device, and which could only be controlled via MQTT messages. Finally, the system is suitable for further upgrades, and in the future the HTTP protocol could be integrated and data stored in a database so that data could be retrieved and managed via web applications or more IoT devices could be added to the system and BLE tested, mesh technology.