The Use of MQTT in M2M and IoT Systems: A Survey

TLDR

The Internet of Things now hosts billions of smart devices that continuously grow, requiring diverse communication protocols to enable secure, bi‑directional data exchange and support applications that collect, store, process, and analyze sensor information. This survey examines the evolution of machine‑to‑machine protocols—MQTT, AMQP, and CoAP—over two decades, highlighting MQTT’s distinctive growth trajectory. We performed a comprehensive literature search to identify MQTT application domains and developed a taxonomy comparing broker and client library properties to aid researchers and users in selecting appropriate implementations. Our quantitative analysis of recent MQTT studies reveals its key features, advantages, and limitations, and identifies open research issues that warrant further investigation.

Abstract

Nowadays billions of smart devices or things are present in Internet of Things (IoT) environments, such as homes, hospitals, factories, and vehicles, all around the world. As a result, the number of interconnected devices is continuously and rapidly growing. These devices communicate with each other and with other services using various communication protocols for the transportation of sensor or event data. These protocols enable applications to collect, store, process, describe, and analyze data to solve a variety of problems. IoT also aims to provide secure, bi-directional communication between interconnected devices, such as sensors, actuators, microcontrollers or smart appliances, and corresponding cloud services. In this paper we analyze the growth of M2M protocol research (MQTT, AMQP, and CoAP) over the past 20 years, and show how the growth in MQTT research stands out from the rest. We also gather relevant application areas of MQTT, as the most widespread M2M/IoT protocol, by performing a detailed literature search in major digital research archives. Our quantitative evaluation presents some of the important MQTT-related studies published in the past five years, which we compare to discuss the main features, advantages, and limitations of the MQTT protocol. We also propose a taxonomy to compare the properties and features of various MQTT implementations, i.e. brokers and libraries currently available in the public domain to help researchers and end-users to efficiently choose a broker or client library based on their requirements. Finally, we discuss the relevant findings of our comparison and highlight open issues that need further research and attention.