Beyond MQTT: Core Protocol Systems for Industrial IoT Platforms

In industrial IoT projects, a frequently underestimated issue is: the device is connected, but the platform cannot 'understand' it. The reason is often simple—the platform only supports MQTT, while the field device uses Modbus, OPC UA, IEC104, or even a proprietary TCP protocol.

A mature IoT platform must have multi-protocol access capabilities to handle the reality of protocol fragmentation in industrial settings.

I. Why is "MQTT-Only" Insufficient?

MQTT, with its lightweight design, low power consumption, and publish/subscribe model, has become the core standard protocol for IoT platforms. It is well-suited for smart hardware, connected vehicles, energy monitoring, and similar applications. However, the complexity of industrial environments far exceeds this.

Industry practice shows that a medium-sized industrial IoT project may involve field devices using 5 to 8 different communication protocols. If the platform only supports MQTT, a large number of devices cannot connect directly, eventually requiring the development of additional protocol gateways and increasing project complexity.

II. Nine Types of Protocols a Mature Platform Should Support

Drawing from mainstream platforms like Huawei Cloud IoTDA and Alibaba Cloud IoT, and considering real-world industrial needs, the following nine types of protocols represent the access capabilities a mature industrial IoT platform should possess:

1. MQTT: The "Lingua Franca" of IoT

Role: The most important standard IoT protocol, suited for data reporting from various sensors and gateways.

MQTT operates over TCP/IP using a publish/subscribe model. It is characterized by a concise message structure, low power consumption, and support for three QoS levels. On the device side, MQTT is the preferred choice for connecting to the cloud, thanks to its mature ecosystem and broad support from cloud platforms.

Use Cases: Smart hardware, connected vehicles, energy monitoring, industrial sensor data reporting.

2. HTTP/HTTPS: The Most Universally Compatible Access Method

Role: Suitable for third-party system integration, web devices, and short-connection data reporting.

HTTP uses a request/response model and is universally supported by almost all programming languages and platforms. For terminals that do not support long connections, making data uploads via HTTP interfaces is the simplest implementation method.

Use Cases: Third-party system integration, periodic data reporting, device management interfaces.

3. TCP and UDP: The Transport Layer for Custom Protocols

Role: TCP offers reliable transmission, while UDP emphasizes transmission efficiency. Both are suitable for transparent transmission of proprietary protocols.

Many industrial devices use manufacturer-specific communication protocols that run directly over TCP or UDP. The platform needs to support raw packet passthrough, leaving protocol parsing to the upper-layer applications.

Use Cases: Retrofitting legacy equipment, integrating vendor-specific protocols, and scenarios demanding high real-time performance like video streaming.

4. Modbus: The "De Facto Standard" in Industrial Settings

Role: The most widely used communication protocol in industrial automation, covering the majority of PLCs, instruments, and sensors.

Modbus exists in serial (RTU/ASCII) and Ethernet (TCP) variants, but the application-layer protocol is identical; only the transport layer differs. Most platforms integrate Modbus via edge gateways or protocol conversion plugins.

Use Cases: PLC data acquisition, smart meter reading (electricity, water, gas).

5. OPC UA: The Core Protocol for Industry 4.0

Role: A future-proof, unified industrial communication architecture supporting secure, cross-platform, cross-network communication.

OPC UA is the next-generation standard, entirely rebuilt from the ground up compared to OPC DA. It supports end-to-end communication from sensors to the cloud. Compared to classic OPC, OPC UA offers significant improvements in security, platform independence, and scalability.

Use Cases: Smart manufacturing, process industry, cross-system data integration.

6. IEC 104: The "International Language" of Power Automation

Role: The most important standard communication protocol in the power and rail transit sectors.

IEC 104 defines data exchange between substations and control centers. It is widely used in renewable energy plants, distribution network automation, and metro power supply systems. Platforms typically require protocol plugins or mirrored implementations for native integration.

Use Cases: Solar/wind farm monitoring, distribution automation, urban rail transit power supervision.

7. CoAP and LwM2M: The "Golden Combination" for Low-Power IoT

Role: Lightweight protocols specifically for resource-constrained devices; CoAP serves as the underlying transport, while LwM2M provides a device management framework.

CoAP is UDP-based with minimal overhead, ideal for low-power WAN scenarios like NB-IoT. LwM2M runs on top of CoAP, defining complete models for device management, data reporting, and firmware upgrades.

Use Cases: Water meters, electricity meters, smart manhole covers, environmental monitoring, and other low-power devices.

8. WebSocket: The "Bidirectional Channel" for Real-Time Web Applications

Role: A full-duplex communication protocol, ideal for browser-based device monitoring and real-time data pushing.

WebSocket establishes persistent connections in browsers, supporting server-push capabilities. It is an excellent choice for web-based SCADA and real-time monitoring dashboards.

Use Cases: Web-based device monitoring, real-time data visualization, remote control consoles.

9. Industry-Specific Protocols (JT/T 808, SL651, HJ212, etc.)

Role: National or industry-specific standards that platforms must support via extension.

III. The Role of MovingComm Industrial Routers in Multi-Protocol Scenarios

In industrial environments characterized by protocol fragmentation, MovingComm's ComIn series industrial routers (such as the I2100 and I5100) serve a dual role as both data conduits and protocol bridges:

Data Aggregation: Simultaneously connect Modbus, PLC proprietary protocols, OPC UA, and other disparate devices via RS485/RS232 serial ports and Ethernet ports to aggregate on-site data.

Protocol Conversion: Convert serial protocols like Modbus RTU into MQTT for upload to cloud platforms over 4G/5G networks, enabling legacy devices to connect to modern IoT ecosystems.

Link Redundancy: Dual SIM and wired WAN redundancy ensure reliable transmission of converted data.

Cloud Coordination: When paired with the MovingComm ComCloud platform, this enables unified management and remote maintenance of multi-protocol devices, eliminating the need for per-device protocol parameter tuning.

IV. Conclusion

The protocol access capability of an IoT platform determines the device coverage and implementation complexity of a project. MQTT is central but far from sufficient. Given the coexistence of Modbus, OPC UA, IEC104, CoAP, and others in industrial settings, the platform must implement a flexible multi-protocol gateway mechanism at the device access layer.

Selecting the right industrial gateway equipment helps project teams address protocol fragmentation at the access layer, allowing engineers to focus more on business logic rather than constantly spending effort on protocol conversion.

This article is based on general IoT platform architectures and practical experience with industrial protocols, intended as a reference for technical professionals. For specific device protocol support, please refer to the respective manufacturers' product specifications. For tailored device selection and project design advice, please contact the MovingComm official technical support team.