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@github-actions github-actions released this 05 Jul 10:47
v1.0.0
220b879

Date: 2026-07-05
Previous release: none

Summary

First release of the Modbus TCP device simulator for gateway integration and CI testing.

  • Fixture-driven simulation — modbus-simulator.fixture.v1 JSON defines one or more devices (coils, discrete inputs, holding/input registers, FC43 identity, exception/fault rules).
  • Stateful runtime — writes persist in memory; optional resetOnConnection per device.
  • JSONL traces — run --trace records modbus-simulator.trace.v1 logs with deterministic seq, responses, and stateChanges.
  • CI assertions — assert-trace evaluates modbus-simulator.expect.v1 files (contains, notContains, count, ordered, exact).
  • CLI — validate, run, assert-trace, version, and shell completion.
  • Schemas — canonical JSON Schemas in schemas/ (fixture-v1.json, trace-v1.json, expect-v1.json), embedded in the binary for offline validation.
  • Examples — ten ready-to-run fixtures in examples/ (one per supported FC plus an all-in-one fixture), each covered by TCP integration tests.
  • License — MIT (LICENSE).

Install

Download the binary for your platform from GitHub Releases, or:

go install github.com/otfabric/modbus-simulator@v1.0.0

Requires Go 1.25+ when building from source.

Pre-built binaries are published for linux/amd64, linux/arm64, linux/arm/v7, darwin/amd64, darwin/arm64, windows/amd64, and windows/arm64.

Breaking changes

None (initial release).

Known limitations (v1)

  • TCP only; RTU/serial server and TCP+TLS listen are deferred.
  • timeout and connectionClose fault rules are recorded in traces but approximated on the wire (go-modbus handler constraints).
  • resetViaControl and reloadFixture state modes are deferred.
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