This paper gives insight on the WebSocket communication method in Internet of Things system, where the hardware part of the system is based on ESP32 microcontroller. Method of implementation is discussed and the reliability of the real-time data transfer in Wi-Fi networks is tested and compared with the long-polling method. Special circuit is designed with the goal to stress the hardware part of the system and the client-server communication link in order to enable proper comparison of data transfer methods. For the comprehensive testing of the real-time data ow, a web server application is designed and used to visualize received data. Impact of RSSI on transfer methods is discussed as well. Eciency of the WebSocket method is discussed and then compared to the long-polling method.