Introduction to Internet of Things (IoT) Protocols

1、Physical connection protocols specify the physical connection methods, transmission media, and interface specifications between devices, primarily categorized as wireless or wired (e.g., RJ45, RS485, RS232, USB). These protocols are analogous to the choice of mail delivery method between individuals—whether by land or air.

2、Transmission Protocols: These protocols primarily manage device networking and communication within subnets, including Ethernet, Wi-Fi, RFID, NFC (Near Field Communication), LoRa/LoRaWAN, NB-IoT, Zigbee, 6LoWPAN (IPv6 Low-Speed Wireless Protocol), GSM, GPRS, GPS, Bluetooth, 3G,4G, and 5G. They define data transmission methods between devices while ensuring security and reliability at the network level. Much like human communication, transmission protocols facilitate information exchange through various channels such as traditional paper mail, telephone, telegraph, email, and WeChat.

3. Communication Protocols: These primarily operate on traditional TCP/IP network protocols (application-layer protocols) and define the message formats for data exchange and communication between devices over networks. Common IoT communication protocols include MQTT, CoAP, and Modbus, which can be categorized into general-purpose protocols and industry-specific protocols. Essentially, communication protocols serve as the organizational framework and grammatical standards for information exchange between individuals, enabling data transmission through various formats such as Chinese, English, Russian, Mandarin/dialects, graphical symbols, audio, and video.

The diagram below provides a more detailed classification of the protocol hierarchy in the Internet of Things (IoT).

The rapid development of the Internet of Things (IoT) has given rise to various communication protocols, each uniquely designed and optimized for different application scenarios and requirements. Below is a detailed analysis of several commonly used communication protocols:

1. MQTT (Message Queuing Telemetry Transport) is a lightweight, publish/subscribe-based messaging protocol designed for device communication in low-bandwidth, high-latency, or unstable network environments. It delivers real-time and efficient message delivery, allowing clients to selectively receive data updates on specific topics while supporting QoS (Quality of Service) levels to ensure reliable transmission. As middleware, MQTT servers (known as Brokers) eliminate the need for direct point-to-point device connections, simplifying system architecture complexity.

2. CoAP (Constrained Application Protocol) is an application-layer protocol designed for resource-constrained IoT devices, built on the UDP framework. It emulates the RESTful interaction model of HTTP but with a more streamlined design, making it ideal for low-power, low-memory sensor networks. CoAP employs a stateless request-response mechanism without maintaining persistent connections, though it can leverage the observer pattern for real-time data streaming when required.

3. Modbus The Modbus protocol, developed by Modicon (now part of Schneider Electric) in 1979, is a communication standard for electronic controllers. As an open and widely adopted industrial protocol, it supports various automation devices including PLCs (Programmable Logic Controllers), sensors, and actuators. With the advancement of the Internet of Things (IoT), Modbus has gained increasing adoption in IoT devices due to its efficient network communication capabilities, enabling applications such as data acquisition, status monitoring, and remote control.

4、REST/HTTP

In IoT scenarios, the traditional HTTP protocol, when integrated with the REST (Representational State Transfer) architecture, provides an easy-to-implement and widely adopted service invocation method. Although HTTP may not outperform MQTT and CoAP in power consumption and bandwidth efficiency, its broad compatibility and mature ecosystem make it a key player in cloud interfaces and device management.