MCP Proxies

A TypeScript library that provides proxy implementations for communication between transport layers of MCP.

Currently supports stdio proxy with Server-Sent Events (SSE) for bidirectional communication.

Usage

Installation

Wherever you have to put the command to run your MCP server, add the following command:

npx -y @indusbit/mcp-proxy stdio

By default, it connects to http://localhost:4000/sse.

Environment Variables

• MCP_SERVER_URL: The URL for the SSE connection
• MCP_LOG_FILE: Path to a log file for debugging (if not set, logging is disabled)

Command Line

After cloning the repository, install dependencies:

npm install

To start the stdio proxy, set the MCP_SERVER_URL environment variable to the base URL of the SSE server:

MCP_SERVER_URL=http://localhost:3000/sse npx . stdio

You can also set the MCP_LOG_FILE environment variable to a path to a log file for debugging:

MCP_SERVER_URL=http://localhost:3000/sse MCP_LOG_FILE=./logs/stdio.log npx stdio

When settign the MCP_LOG_FILE environment variable in an MCP client (like claude), don't forget to provide it a full path.

Proxy Types

stdio

The stdio proxy establishes a bidirectional communication channel between standard input/output and a server using Server-Sent Events (SSE):

1. Connects to an SSE endpoint specified by MCP_SERVER_URL (defaults to "http://localhost:4000/sse")
2. Receives a messaging endpoint from the server via an "endpoint" event
3. Forwards messages from stdin to the server via HTTP POST requests
4. Forwards messages from the server to stdout

Configuration

The following environment variables can be used to configure the proxies:

• MCP_SERVER_URL: The base URL for the SSE connection (default: "http://localhost:4000/sse")
• MCP_LOG_FILE: Path to a log file for debugging (if not set, logging is disabled)

Development

Building

npm run build

License

MIT