modbus-mcp

An MCP server that standardizes and contextualizes industrial Modbus data.

18 stars PythonServers & Infrastructure Updated Oct 18, 2025

Documentation

Modbus MCP Server

An MCP server that standardizes and contextualizes Modbus data, enabling seamless integration of AI agents with industrial IoT systems.

Features

Modbus Tools:
- Read/write holding registers (`read_register`, `write_register`).
- Read/write coils (`read_coils`, `write_coil`).
- Read input registers (`read_input_registers`).
- Read multiple holding registers (`read_multiple_holding_registers`).
Prompt: Analyze Modbus register values with a customizable prompt (`analyze_register`).
Flexible Connections: Supports Modbus over TCP, UDP, or serial, configured via environment variables.

Requirements

Python: 3.10
uv for dependency and virtual environment management.

Installation

1. Install `uv`:

bash

curl -LsSf https://astral.sh/uv/install.sh | sh

2. Clone the Repository:

bash

git clone https://github.com/kukapay/modbus-mcp.git
   cd modbus-mcp

3. Install Dependencies:

bash

uv sync

Configuration

The server connects to a Modbus device using parameters specified via environment variables. Set these variables in a `.env` file or your shell environment.

Environment Variables

Variable	Description	Default	Required
`MODBUS_TYPE`	Connection type: `tcp`, `udp`, or `serial`	`tcp`	Yes
`MODBUS_HOST`	Host address for TCP/UDP	`127.0.0.1`	For TCP/UDP
`MODBUS_PORT`	Port for TCP/UDP	`502`	For TCP/UDP
`MODBUS_DEFAULT_SLAVE_ID`	Slave ID	`1`	For TCP/UDP
`MODBUS_SERIAL_PORT`	Serial port (e.g., `/dev/ttyUSB0`, `COM1`)	`/dev/ttyUSB0`	For serial
`MODBUS_BAUDRATE`	Serial baud rate	`9600`	For serial
`MODBUS_PARITY`	Serial parity: `N` (none), `E` (even), `O` (odd)	`N`	For serial
`MODBUS_STOPBITS`	Serial stop bits	`1`	For serial
`MODBUS_BYTESIZE`	Serial byte size	`8`	For serial
`MODBUS_TIMEOUT`	Serial timeout (seconds)	`1`	For serial

Example `.env` File

For TCP:

code

MODBUS_TYPE=tcp
MODBUS_HOST=192.168.1.100
MODBUS_PORT=502
MODBUS_SLAVE_ID=1

For Serial:

code

MODBUS_TYPE=serial
MODBUS_SERIAL_PORT=/dev/ttyUSB0
MODBUS_BAUDRATE=9600
MODBUS_PARITY=N
MODBUS_STOPBITS=1
MODBUS_BYTESIZE=8
MODBUS_TIMEOUT=1

Usage

Installing for Claude Desktop

The configuration file:

json

{
   "mcpServers": {
       "Modbus MCP Server": {
           "command": "uv",
           "args": [ "--directory", "/path/to/modbus-mcp", "run", "modbus-mcp" ],
           "env": { "MODBUS_TYPE": "tcp", "MODBUS_HOST": "127.0.0.1", "MODBUS_PORT": 502 },
       }
   }
}

Using Tools

Note: Natural language support depends on the client’s ability to parse and map prompts to tools. The MCP Inspector requires structured JSON, but the examples below show how conversational inputs translate.

1. Read a Holding Register:

code

Please read the value of Modbus holding register 0.

json

{
       "tool": "read_register",
       "parameters": {"address": 0, "slave_id": 1}
     }

2. Write to a Holding Register:

code

Set Modbus holding register 10 to the value 100.

json

{
       "tool": "write_register",
       "parameters": {"address": 10, "value": 100, "slave_id": 1}
     }

3. Read Coils:

code

Check the status of the first 5 Modbus coils starting at address 0.

json

{
       "tool": "read_coils",
       "parameters": {"address": 0, "count": 5, "slave_id": 1}
     }

4. Write to a Coil:

code

Turn on Modbus coil 5.

json

{
       "tool": "write_coil",
       "parameters": {"address": 5, "value": true, "slave_id": 1}
     }

5. Read Input Registers:

code

Read the values of 3 Modbus input registers starting from address 2.

json

{
       "tool": "read_input_registers",
       "parameters": {"address": 2, "count": 3, "slave_id": 1}
     }

6. Read Multiple Holding Registers:

code

Get the values of Modbus holding registers 0 through 2.

json

{
       "tool": "read_multiple_holding_registers",
       "parameters": {"address": 0, "count": 3, "slave_id": 1}
     }

License

This project is licensed under the MIT License. See LICENSE for details.

Frequently asked questions

What is modbus-mcp?

modbus-mcp is An MCP server that standardizes and contextualizes industrial Modbus data.

How do I install modbus-mcp?

Open the GitHub repository and follow its README. Most MCP servers are added to your client's MCP config, then called by your agent.

Is modbus-mcp open source?

Yes — it is hosted on GitHub at https://github.com/kukapay/modbus-mcp and has 18 stars.

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