How to Use Node-RED as a Modbus TCP Server (Without Writing Custom Code)

#nodered #modbus #iot #industrial

If you’ve worked with industrial systems, you’ve almost certainly encountered Modbus TCP.

It’s reliable, widely supported, and still heavily used across PLCs, meters, and industrial controllers. At the same time, building or simulating a Modbus server often feels more complex than it should—especially when the goal is integration testing or edge gateway development.

Many teams default to writing custom Modbus servers just to expose registers or simulate devices. In practice, this approach often slows projects down.

Node-RED as a Modbus Server

Node-RED is usually associated with low-code automation, but in industrial IoT projects, it can serve as a powerful middleware layer.

With the right setup, Node-RED can:

Run as a Modbus TCP server
Expose virtual Modbus registers
Simulate industrial devices before hardware is available
Bridge Modbus data into MQTT, HTTP, or cloud platforms

This makes it especially useful for edge gateways, industrial protocol bridging, and early-stage integration testing.

Typical Use Cases

This approach is commonly used in scenarios such as:

Factory or system integration testing
Industrial IoT gateways aggregating Modbus data
Proof-of-concept environments for SCADA or MES systems
Legacy device integration with modern IoT platforms

Instead of building everything from scratch, Node-RED allows teams to validate communication flows early and iterate faster.

Looking for the Actual Configuration Steps?

This post intentionally avoids pasting full configurations or screenshots. In real Modbus projects, small details—such as address offsets, register types, and connection modes—often make or break a setup.

The complete tutorial walks through:

Running Node-RED in Modbus TCP server mode
Defining and updating holding and input registers correctly
Testing communication with real Modbus client tools
Debugging common connection and data consistency issues

👉 Full step-by-step walkthrough (with screenshots):

https://zediot.com/blog/node-red-modbus-server-guide/

If you’re building or testing industrial IoT gateways, this guide can save you a lot of trial and error.

About ZedIoT

ZedIoT builds and integrates industrial IoT and edge solutions, with a focus on Node-RED workflows, Modbus-based systems, and device-to-cloud integration.

We work with teams that need reliable bridges between legacy industrial protocols and modern IoT platforms.