MCP Proxy Sidecar

A fork of the JetBrains MCP Server that adds WebSocket monitoring capabilities, created by @dortegau.

This project extends the original MCP server functionality with WebSocket support while maintaining compatibility with all features of the original implementation.

Architecture

graph LR
    A[MCP Client<br>e.g. Claude<br>Desktop App]
    B[MCP Proxy<br>Sidecar<br>with WebSocket]
    C[JetBrains IDE]
    D[WebSocket Clients<br>Monitoring]
    
    A <--MCP requests/responses--> B
    B <--IDE commands/responses--> C
    B --WebSocket notifications<br>port 27042--> D

    style A fill:#f5f5f5,stroke:#333,stroke-width:2px
    style B fill:#e1f5fe,stroke:#333,stroke-width:2px
    style C fill:#f5f5f5,stroke:#333,stroke-width:2px
    style D fill:#f5f5f5,stroke:#333,stroke-width:2px

The diagram above illustrates the system architecture and data flow:

MCP Clients (like Claude Desktop App) communicate with the Sidecar using MCP protocol
The Sidecar translates and forwards commands to JetBrains IDE
Responses from the IDE are sent back through the Sidecar
All tool calls are broadcasted via WebSocket for monitoring purposes

Features

This fork adds WebSocket notifications that allow you to monitor all MCP tool calls in real-time. Each tool call is broadcasted through WebSocket with detailed information about the endpoint and arguments.

WebSocket Message Format

interface MCPNotification {
  type: 'mcp-notification';
  payload: {
    endpoint: string;     // Tool name that was called
    content: any;         // Call arguments
    timestamp: string;    // ISO timestamp
  }
}

WebSocket Configuration

The WebSocket server runs on port 27042 by default. You can customize this port using the WS_PORT environment variable in your configuration:

"env": {
  "WS_PORT": "<custom port number>"  // Example: "8080"
}

Usage

Install MCP Server Plugin

https://plugins.jetbrains.com/plugin/26071-mcp-server

Usage with Claude Desktop

To use this with Claude Desktop, add the following to your claude_desktop_config.json. The full path on MacOS: ~/Library/Application\ Support/Claude/claude_desktop_config.json, on Windows: %APPDATA%/Claude/claude_desktop_config.json.

{
  "mcpServers": {
    "ide": {
      "command": "npx",
      "args": ["-y", "mcp-proxy-sidecar"],
      "env": {
        "WS_PORT": "27042"  // Optional: customize WebSocket port
      }
    }
  }
}

Configuration Options

The following environment variables can be configured in your claude_desktop_config.json:

Variable	Description	Default
`WS_PORT`	Port for WebSocket server	`27042`
`IDE_PORT`	Specific port for IDE connection	Auto-scans 63342-63352
`HOST`	Host address for IDE connection	`127.0.0.1`
`LOG_ENABLED`	Enable debug logging	`false`

Example configuration with all options:

{
  "mcpServers": {
    "ide": {
      "command": "npx",
      "args": ["-y", "mcp-proxy-sidecar"],
      "env": {
        "WS_PORT": "27042",
        "IDE_PORT": "63342",
        "HOST": "127.0.0.1",
        "LOG_ENABLED": "true"
      }
    }
  }
}

Note: If IDE_PORT is not specified, the sidecar will automatically scan ports 63342-63352 to find the IDE.

Development

Requirements

Node.js 20.x
pnpm (latest version)

Build

Install dependencies:
```
pnpm install --frozen-lockfile
```
Build the project:
```
pnpm build
```

Contributing

Fork the repository
Create your feature branch (git checkout -b feature/amazing-feature)
Commit your changes (git commit -m 'Add some amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

Publishing

This package is published to npm with:

Provenance enabled for supply chain security
Automated releases via GitHub Actions when creating a new release
Public access on npm registry

To publish a new version:

Update version in package.json
Create and push a new tag matching the version
Create a GitHub release from the tag
The workflow will automatically build and publish to npm

Changelog

1.0.0

Initial fork from @jetbrains/mcp-proxy
Added WebSocket support for real-time tool call monitoring
Renamed package for clarity
Updated documentation and configuration examples

Credits

This is a fork of the JetBrains MCP Proxy Server. All credit for the original implementation goes to the JetBrains team.