MCP SSE demo

by the-vampiire

Meta/Examples SSE bun nodejs server-sent-events demo

This is a reproducible demo that shows an MCP SSE server failing using the bun runtime but succeeding using Node.js. It provides steps to reproduce the issue and observe the network behavior.

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What is MCP SSE demo?

This is a demonstration server for MCP (presumably Message Channel Protocol) using Server-Sent Events (SSE). It highlights a compatibility issue between the bun runtime and the server's SSE implementation.

How to use MCP SSE demo?

Install dependencies using bun install. 2. Run the MCP inspector using npm run inspect. 3. Open the inspector in a browser. 4. Select SSE as the transport and enter http://localhost:3500/sse as the URL. 5. Open the browser's dev tools network tab. 6. Run the server using bun (npm run start:bun) and observe the failed connection. 7. Kill the bun server and run the server using Node.js (npm run start:node) and observe the successful connection.

Key features of MCP SSE demo

Demonstrates SSE server behavior
Reproducible bug report
Comparison between bun and Node.js runtimes
Uses MCP inspector for testing

Use cases of MCP SSE demo

Debugging SSE server implementations
Testing runtime compatibility
Reproducing bug reports
Understanding SSE connection behavior

FAQ from MCP SSE demo

Why does the server fail with bun?

The README doesn't provide a specific reason, but it demonstrates that bun's SSE implementation has issues with this particular server setup.

What is the MCP inspector?

The README doesn't explain what the MCP inspector is, but it's used as a client to connect to the SSE server.

What dependencies are required?

The README mentions using bun install, so it likely requires dependencies defined in a package.json file.

Is this a production-ready server?

No, this is a demonstration server intended for reproducing a specific issue.

Where can I find the server's code?

The server's code is available in the linked GitHub repository.