Modbus Simulator v0.1.0 — first release

The first OpenBench tool is live. The Modbus Simulator is a free, open-source utility for exercising Modbus TCP and RTU without real hardware — either as a simulated device (slave) or as a polling client (master).

Why build another Modbus simulator

The commercial ones work. They’re also closed-source and licensed per seat, which is real friction when you just need to confirm a register map before a site visit, or when your company’s security policy wants a tool audited before it goes on an engineering workstation. This does the same job, free, with the source open.

What’s in v0.1.0

• Slave mode — the app answers requests from an editable register table. Type a value in, and a connected client reads it back; incoming writes land in the table and the log.
• Master mode — point it at a device, pick a table and address range, and it polls on an interval. Results mirror into the table live; editing a value sends a write.
• Modbus TCP and Modbus RTU over serial, client and server, switchable at runtime.
• All four tables (coils, discrete inputs, holding & input registers) across the full 0–65535 address space.
• Function codes 0x01–0x06, 0x0F, 0x10, with spec-correct exception responses.
• A live traffic log — every frame with timestamp, direction, function, decoded values, and raw ADU bytes — exportable as CSV.

No license key, no telemetry, no network calls of its own.

Get it

A single self-contained Windows executable, no installer or .NET runtime required. Download it from the tool page, or grab it straight from the GitHub release. The documentation covers install and quick starts for both TCP and RTU.

Known limitations

• The RTU/serial path has been exercised in loopback tests only, not yet against physical hardware. If you run it on a real bus, feedback is welcome.
• Windows x64 only for now; a Linux build works from source.
• Not code-signed, so SmartScreen will warn on first run.

What’s next

More testing against real devices, a configurable RTU inter-frame gap, and — depending on what people actually ask for — either a serial-line terminal or a TCP/IP tester as the second tool. If you have opinions, the GitHub Discussions are open.