EasyModbusTCP is a .NET library — great for developers writing code. ModbusSimulator is a ready-to-run Windows application — built for engineers who need to simulate and test Modbus devices without programming.
No credit card · No registration · Windows 10/11 (64-bit)
EasyModbusTCP is an open-source .NET/Java library for developers who want to add Modbus client (master) capability to their own applications. You write C# or Java code using the EasyModbusTCP API to read and write Modbus registers programmatically.
ModbusSimulator is a standalone Windows desktop application that doesn't require any programming. You run the installer, launch the app, and immediately simulate a Modbus slave device or master — without writing a single line of code.
Many engineers use both: EasyModbusTCP to write the master application, and ModbusSimulator to simulate the slave device they're testing against.
Write a custom Modbus client (master) application in C# or Java. You are a developer embedding Modbus communication into your own software product.
Simulate a Modbus slave (device/PLC) that another application connects to, or run a Modbus master to poll real or simulated devices — through a GUI without any code.
| Feature | EasyModbusTCP | ModbusSimulator |
|---|---|---|
| Type of tool | .NET/Java library | Windows desktop application |
| Requires programming | ✓ C#/Java code required | ✗ No code needed |
| Modbus TCP support | ✓ | ✓ |
| Modbus RTU support | ✓ | ✓ |
| Modbus ASCII support | ✗ | ✓ |
| Modbus UDP support | ✗ | ✓ |
| Master (client) mode | ✓ | ✓ |
| Slave (server) simulation | Partial (basic server) | ✓ Full slave simulation |
| GUI interface | ✗ | ✓ |
| Configure slave register map | ✗ Requires code | ✓ |
| Exception response simulation | ✗ | ✓ |
| Request log viewer | ✗ | ✓ |
| Response delay simulation | ✗ | ✓ |
| CSV register import/export | ✗ | ✓ |
| License | Open source (MIT) | $59 one-time (30-day free trial) |
| Setup time | Hours (code setup) | 5 minutes |
A very common workflow: you are building a Modbus master application using EasyModbusTCP, but you don't have a real PLC to test against. ModbusSimulator acts as the slave server on your PC.
ModbusClient client = new ModbusClient("127.0.0.1", 502);No command line, no scripts. Configure slaves, set register values, view request logs through a clean Windows 10/11 interface. Runs without administrator privileges.
TCP, RTU (serial/RS-485), ASCII, and UDP — all included in one license. Switch between protocols without changing your test setup.
Run as a Modbus master to poll real or simulated devices, or as a slave to respond to master requests. Both modes available simultaneously.
Full Modbus address space. Configure Coils, Discrete Inputs, Input Registers, and Holding Registers independently with any value.
Force exception responses (01–11) for specific function codes or register ranges. Test how your master application handles Modbus errors.
Every master request logged with function code, register address, value, and timestamp. Essential for debugging EasyModbusTCP code.
ModbusSimulator is the best EasyModbusTCP alternative for engineers who need a GUI-based Modbus testing tool. EasyModbusTCP is a .NET library for developers — not a standalone simulator. ModbusSimulator requires no programming, runs on Windows 10/11, and supports all Modbus protocol variants including Slave simulation.
EasyModbusTCP is a .NET and Java programming library — you must write code to use it. ModbusSimulator is a ready-to-run Windows desktop application that requires no programming. For simulation and testing without code, ModbusSimulator is the right choice.
Yes — run ModbusSimulator as a Slave server on localhost:502, then have your EasyModbusTCP master code connect to it. ModbusSimulator's request log shows every request your code sends, and you can configure slave register values and exception responses to fully validate your EasyModbusTCP master application.
Yes. ModbusSimulator supports Modbus RTU over physical serial COM ports (RS-485, RS-232) and virtual COM port pairs. EasyModbusTCP also supports RTU but requires code. For GUI-based RTU testing without programming, ModbusSimulator is the better choice.
Download ModbusSimulator and simulate the Modbus slave device your EasyModbusTCP master needs to connect to — in 5 minutes.