Modbus TCP is an industrial communication protocol used to exchange data between devices on a network. It connects PLCs, sensors, drives, and other equipment to SCADA systems and HMI displays.

Do I need hardware to practice Modbus?

No. IT OT Lab simulates Modbus TCP devices in the cloud. You practice with real protocols and register maps in your browser — no PLCs, no wiring, no licenses.

An HMI (Human-Machine Interface) is an operator dashboard used to monitor and control industrial processes. IT OT Lab includes FUXA, an open-source HMI editor where you build screens with gauges, charts, and controls connected to simulated Modbus devices.

Practice industrial protocols.
No hardware required.

A browser-based training lab for Modbus TCP, SCADA, and HMI development. Simulated devices, real protocols, full register maps.

Launch the Lab See what's inside

modbus-read · Bay 1, Unit 1

$ read holding 0-12, unit 1

reg[0] status 1 loading

reg[1] bay 1

reg[2] gross_gal 3847.5 float32

reg[4] net_gal 3845.1 float32

reg[6] flow_gpm 598.3 float32

reg[8] temp_f_x10 651 ×0.1 = 65.1°F

reg[9] density 745.2 float32

reg[11] alarm_code 0 none

reg[12] heartbeat 4218

Components

Three tools, one lab

Everything runs in the cloud. Students open a browser and start working — nothing to download or install.

Data Maker

Modbus TCP device simulator with a web-based editor. Loading bays, linked storage tanks, configurable register maps, fault injection, and real-time state machines.

lab.itotlab.com

FUXA HMI

Open-source SCADA/HMI editor. Build dashboards with gauges, charts, and controls. Connect to simulated Modbus devices and visualize live process data.

hmi.itotlab.com

Modbus TCP

Real Modbus protocol on port 5020. Multiple unit IDs, holding registers, coils, and standard data types. Compatible with any Modbus client or polling tool.

pymodbus 3.6.9

Register	Name	Type	Description
0	status	uint16	0 = idle, 1 = loading, 2 = complete, 3 = alarm
1	bay	uint16	Bay number
2–3	gross_gal	float32	Gross gallons loaded this batch
4–5	net_gal	float32	Temperature-corrected net gallons
6–7	flow_gpm	float32	Current flow rate in GPM
8	temp_f_x10	int16	Temperature (°F × 10)
9–10	density	float32	Product density (kg/m³)
11	alarm_code	uint16	Active alarm (0 = none, 5 = high temp, 6 = tank empty)
12	heartbeat	uint16	Increments each tick (0–65535)
100	stop_cmd	uint16	Write 1 to stop current batch

How it works

From zero to reading registers in 60 seconds

No installs, no configuration files, no licensing. The lab is always on.

Open the lab

Go to lab.itotlab.com. Enter your email and a one-time code. You're in.

Explore the devices

The Data Maker runs four loading bays and two linked storage tanks. Register values update in real time as bays load and tanks drain.

Build an HMI

Open the FUXA editor and connect to Modbus devices. Drag in gauges, trend charts, and controls.

Inject faults

Trigger word-swap errors, sensor freezes, and equipment failures. Practice troubleshooting like you would on a real plant floor.

Use cases

Built for training, ready for practice

Instructor-led training

Run a class with a shared lab environment. All students work against the same simulated plant. No hardware to ship or maintain.

Self-paced learning

Students log in on their own time and follow structured lab exercises. Practice Modbus reads, HMI design, and fault diagnosis.

IT/OT integration

Bridge the gap between IT and OT teams. Practice reading industrial data, understanding register maps, and building operator interfaces.

Security training

Study Modbus protocol behavior, inject faults, and observe how bad data propagates through HMI displays.

Practice industrial protocols.No hardware required.