A Survey of Communication Protocols in IoT: MQTT, COAP, and Beyond

The Internet of Things (IoT) is rapidly revolutionizing industries and everyday life through the integration of smart devices, sensors, and networks. The ability to connect and communicate between these devices is vital for the effective functioning of IoT systems. As IoT devices vary widely in terms of their power, connectivity, and computational capabilities, communication protocols play a crucial role in ensuring seamless, efficient, and reliable communication. Among the most widely used protocols in IoT are MQTT (Message Queuing Telemetry Transport) and CoAP (Constrained Application Protocol), designed to address the specific requirements of IoT, including low power consumption, minimal bandwidth usage, and scalability. This paper surveys the key communication protocols used in IoT, with a specific focus on MQTT and CoAP. It discusses their architecture, characteristics, advantages, and limitations. Furthermore, the paper explores other emerging protocols that complement or extend the capabilities of MQTT and CoAP, such as HTTP/2, LwM2M, and AMQP, providing a broad perspective on the evolving IoT communication landscape. The primary objective of this paper is to evaluate the suitability of these protocols for different IoT applications, ranging from home automation and healthcare to industrial IoT (IIoT). We also highlight the security challenges associated with these protocols and suggest potential solutions. Lastly, we discuss future trends and the need for interoperability between different IoT communication protocols as IoT continues to scale and evolve. By analyzing the strengths and weaknesses of these communication protocols, this paper aims to provide IoT developers, researchers, and industry professionals with valuable insights into selecting the most appropriate communication framework for their IoT systems.