The invention discloses a method of reducing Denial of Service (DoS) attack in an Internet of Things (IoT) system. The method provides real time communication between a sender node and receiver node by multiplexing control channel (that uses voice traffic) and data channel (that uses internet protocol traffic). Further an IoT system is disclosed. The communication channel between the sender node and the receiver node is configured to divide into a control channel to perform a handshake to the receiver node and data channel to carry data. Also to prevent DoS attack ports are changed periodically using the control channel. The advantages include reduced DoS attack in the network, low memory footprint of less than 2 KB and the communication is real time. The system and method may be used in commercial IoT deployments like environmental monitoring, smart grid, smart cities and health care.