The final paper describes how the IoT (Internet of Things) has evolved throughout history, why its application is important and how much data it generates on the Internet. Basic information on why IoT is needed in industry, but also in the personal use of users, and the problems that arise due to security itself are described. The impact of the new fifth generation mobile network (5G) on IoT systems is briefly reviewed and commented on. The advantages and disadvantages of the application are described at the end of the IoT chapter. The MQTT protocol (Message Queue Telemetry Transport), which is later practically implemented, is discussed below, and its functions and working principle are explained. It looks in more detail at the meaning of the client, the broker, the way it connects with the broker and maintains the connection, the quality of service (QoS) and other important parameters of the MQTT protocol. In addition to the practical part of the paper, the Arduino system is described, which is an existing machine / device to which the Esp8266 module is upgraded to become part of the IoT world. The following describes in detail the sensors used and their specifications, as well as part of the program code for their control. Temperature, humidity, pressure sensors as well as a fan were used to demonstrate control and monitoring. The implementation of the MQTT protocol on the Esp8266 module and the application of UART communication, which is the basis of data exchange between the Arduino development platform and the Esp8266 microcontroller itself, are described. In addition to the practical part of the final work, using the Paho library, an Android MQTT mobile application for system monitoring and management was created, and parts of the application were further explained.