OPC UA Server

A Python application that connects to an OPC UA server and exposes it via MCP (Model Context Protocol) using FastMCP.

Features

• Connect to any OPC UA server with optional authentication
• Browse the complete node tree from a configurable starting node
• Expose the OPC UA node tree as MCP resources
• Read values from OPC UA nodes
• Search nodes by display name or browse name with wildcard support
• Support for both stdio and SSE (Server-Sent Events) transport methods

Installation

pip install -r requirements.txt

Usage

Basic usage with HTTP transport (default):

python opcua_mcp_server.py opc.tcp://localhost:4840

With authentication:

python opcua_mcp_server.py opc.tcp://localhost:4840 --username myuser --password mypass

Using stdio transport:

python opcua_mcp_server.py opc.tcp://localhost:4840 --transport stdio

With custom starting node and HTTP port:

python opcua_mcp_server.py opc.tcp://localhost:4840 --start-node "i=84" --http-port 8080

Command Line Arguments

• opcua_url (required): OPC UA server URL (e.g., opc.tcp://localhost:4840)
• --start-node: Starting node ID for browsing (default: i=85)
• --username: Username for OPC UA authentication
• --password: Password for OPC UA authentication
• --transport: MCP transport method - 'stdio' or 'http' (default: http)
• --http-port: Port for HTTP transport (default: 3000)

MCP Tools

The server provides the following tools:

read-value

Read the current value of one or more OPC UA nodes.

Parameters:

• node_ids: List of node IDs to read

Example:

{
  "node_ids": ["ns=2;s=MyVariable", "ns=2;s=Temperature"]
}

find-by-display-name

Find nodes by display name pattern (supports wildcards).

Parameters:

• pattern: Display name pattern with wildcards (e.g., Temperature)

Example:

{
  "pattern": "*Temperature*"
}

find-by-browse-name

Find nodes by browse name pattern (supports wildcards).

Parameters:

• pattern: Browse name pattern with wildcards (e.g., Sensor)

Example:

{
  "pattern": "*Sensor*"
}

Node Information

Each node in the tree contains:

• node_id: The OPC UA node identifier
• browse_name: The browse name of the node
• display_name: The human-readable display name
• node_class: The type of node (e.g., Object, Variable, Method, etc.)
• children: List of child nodes (only for non-leaf nodes)

Example

1. Start an OPC UA server (e.g., using opcua-asyncio example server)
2. Run the MCP server:

   python opcua_mcp_server.py opc.tcp://localhost:4840
   

3. The MCP server will connect to the OPC UA server, browse the node tree, and expose it via MCP
4. You can now use any MCP client to interact with the OPC UA data

Error Handling

• The server will exit if it cannot connect to the OPC UA server
• Individual node read errors are returned in the response
• The server properly disconnects from the OPC UA server on shutdown