allexd2010/modbus-server-sim repository overview

⁠Modbus TCP Server Simulation

Version 2.2.0 — lightweight Modbus TCP simulator with a single in-memory store, a modern Web UI, REST API, Swagger, MCP over HTTP, JavaScript simulation scripts, and a named address map.

Built with Rust (Rocket, tokio-modbus, QuickJS, rmcp).

⁠Features

• Modbus TCP — holding & input registers, coils, discrete inputs (zero-based addressing)
• Web UI at /ui/ — register matrix, UInt16/Int32/float/double, bit masks, auto-refresh; EN/RU; installable PWA
• Address map — named variables (conf/var-map.json), including bit fields in register words
• Simulation scripts — QuickJS rules in /app/script: modbus.onWrite, modbus.setInterval, typed I/O, map.* API
• REST API — /api/v1/ (same data as Modbus TCP)
• Swagger — /api/v1/swagger/
• MCP — Streamable HTTP at /mcp (Modbus tools, var-map, scripts, combined export/import)
• Structured logging — RUST_LOG (default info)

⁠Quick start

docker pull allexd2010/modbus-server-sim:2.2.0

docker run -d --name modbus-sim \
  -p 9090:9090 \
  -p 502:502 \
  -e RUST_LOG=info \
  allexd2010/modbus-server-sim:2.2.0

Open http://localhost:9090/ui/⁠ after start.

⁠Persistent configuration (volumes)

docker run -d --name modbus-sim \
  -p 9090:9090 -p 502:502 \
  -v /path/to/scripts:/app/script \
  -v /path/to/conf:/app/conf \
  allexd2010/modbus-server-sim:2.2.0

• /app/script — simulation *.js files
• /app/conf — var-map.json (named Modbus variables)

⁠Environment variables

⁠Modbus addressing

Protocol and API use zero-based offsets (first holding register = 0).
Modicon-style: 40001 → offset 0, 40021 → offset 20.

⁠MCP example (mcp.json)

{
  "mcpServers": {
    "modbus-tcp-sim": {
      "url": "http://127.0.0.1:9090/mcp"
    }
  }
}

⁠Tags

• 2.2.0 — current release (address map, simulation scripts, structured logging)
• latest — latest stable release
• test — CI builds from main

Release tags are published for linux/amd64 and linux/arm64.

⁠Links

• Source: GitHub⁠
• License: MIT