Invalid transport type specified

[liu-collab]

Describe the bug

import express from "express";
import {
  McpServer,
  ResourceTemplate,
} from "@modelcontextprotocol/sdk/server/mcp.js";
import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
import { z } from "zod";

const server = new McpServer({
  name: "example-server",
  version: "1.0.0",
});

server.tool("add", { a: z.number(), b: z.number() }, async ({ a, b }) => ({
  content: [{ type: "text", text: String(a + b) }],
}));

// Add a dynamic greeting resource
server.resource(
  "greeting",
  new ResourceTemplate("greeting://{name}", { list: undefined }),
  async (uri, { name }) => ({
    contents: [
      {
        uri: uri.href,
        text: `Hello, ${name}!`,
      },
    ],
  })
);

const app = express();

app.get("/sse", async (req, res) => {
  const transport = new SSEServerTransport("/messages", res);
  await server.connect(transport);
});

// app.post("/messages", async (req, res) => {
//   const transport = new SSEServerTransport("/messages", res);

//   // Note: to support multiple simultaneous connections, these messages will
//   // need to be routed to a specific matching transport. (This logic isn't
//   // implemented here, for simplicity.)
//   await transport.handlePostMessage(req, res);
// });

app.listen(3000);

npx @modelcontextprotocol/inspector index.js
Expected behavior
not working

Logs

$ npx @modelcontextprotocol/inspector index.js
Starting MCP inspector...
Proxy server listening on port 3000

🔍 MCP Inspector is up and running at http://localhost:5173 🚀
New SSE connection
Query parameters: { transportType: 'sse', url: 'http://localhost:3000/sse' }
sse transportType
SSE transport: url=http://localhost:3000/sse, headers=
New SSE connection
Query parameters: {}
undefined transportType
Invalid transport type: undefined
undefined transportType
Error in /sse route: Error: Invalid transport type specified
    at createTransport (file:///C:/Users/Administrator/AppData/Local/npm-cache/_npx/5a9d879542beca3a/node_modules/@modelcontextprotocol/inspector/server/build/index.js:74:15)
    at file:///C:/Users/Administrator/AppData/Local/npm-cache/_npx/5a9d879542beca3a/node_modules/@modelcontextprotocol/inspector/server/build/index.js:82:44
    at Layer.handle [as handle_request] (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\route.js:149:13)
    at Route.dispatch (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\route.js:119:3)
    at Layer.handle [as handle_request] (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\layer.js:95:5)
    at C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\index.js:284:15  
    at Function.process_params (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\index.js:346:12)
    at next (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\express\lib\router\index.js:280:10)
    at cors (C:\Users\Administrator\AppData\Local\npm-cache\_npx\5a9d879542beca3a\node_modules\cors\lib\index.js:188:7)      
Error in /sse route: SseError: SSE error: Non-200 status code (500)
    at _eventSource.onerror (file:///C:/Users/Administrator/AppData/Local/npm-cache/_npx/5a9d879542beca3a/node_modules/@modelcontextprotocol/sdk/dist/esm/client/sse.js:69:31)
    at EventSource.failConnection_fn (file:///C:/Users/Administrator/AppData/Local/npm-cache/_npx/5a9d879542beca3a/node_modules/eventsource/dist/index.js:234:53)
    at file:///C:/Users/Administrator/AppData/Local/npm-cache/_npx/5a9d879542beca3a/node_modules/eventsource/dist/index.js:76:74
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {
  code: 500,
  event: {
    type: 'error',
    message: 'Non-200 status code (500)',
    code: 500,
    defaultPrevented: false,
    cancelable: false,
    timeStamp: 8331.5268
  }
}

Additional context
Add any other context about the problem here.