SSEServerTransport can not work

[wyyufeng]

Describe the bug
I write a demo for get document, but the sse server not work well.

To Reproduce
this is my code

import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import {
    CallToolRequestSchema,
    JSONRPCMessage,
    ListResourcesRequestSchema,
    ListToolsRequestSchema,
    ReadResourceRequestSchema,
} from "@modelcontextprotocol/sdk/types.js";
import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
import express from "express";
// import { getDocument } from './fs-docs.js'

const app = express();

const server = new Server(
    {
        name: "boiling-insights",
        version: "0.1.0",
    },
    {
        capabilities: {
            resources: {},
            tools: {},
            // prompts: {},
            templates: {},
        },
    }
);

const SCHEMA_PATH = "schema";
const PORT = 8808;




server.setRequestHandler(ReadResourceRequestSchema, async (request) => {
    const resourceUrl = new URL(request.params.uri);
    const pathComponents = resourceUrl.pathname.split("/");
    const comps = [...pathComponents];
    const schema = pathComponents.pop();
    const document_id = pathComponents.pop();

    if (schema !== SCHEMA_PATH || !document_id) {
        throw new Error("Invalid resource URI");
    }

    try {
        //  get document content 
        const result = await getDocument(document_id);

        return {
            contents: [
                {
                    uri: request.params.uri,
                    mimeType: "text/markdown",
                    text: result,
                },
            ],
        };
    } catch (err) {
        console.error(err);
        throw err;
    }
});

;

server.setRequestHandler(CallToolRequestSchema, async (request) => {
    try {
        const tool = request.params.name;
        if (tool === "getDocument") {
            // console.log(request.params);
            const result = await getDocument(request.params.arguments?.sql as string);
            return {
                content: [{ type: "text", text: result }],
                isError: false,
            };
        } else {
            throw new Error(`Unknown tool: ${request.params.name}`);
        }
    } catch (err) {
        console.error(err);
        throw err;
    }
});

export async function runMCPServer() {
    let transport: SSEServerTransport;

    app.get("/sse", async (req, res) => {
        console.log("--> Received connection:", req.url);
        transport = new SSEServerTransport("/message", res);
        console.log("New SSE connection.");
        await server.connect(transport);
        const _onMsg = transport.onmessage; // original hook
        const _onClose = transport.onclose;
        const _onErr = transport.onerror;
        transport.onmessage = (msg: JSONRPCMessage) => {
            console.log(msg);
            if (_onMsg) _onMsg(msg);
        };
        transport.onclose = () => {
            console.log("Transport closed.");
            if (_onClose) _onClose();
        };
        transport.onerror = (err) => {
            console.error(err);
            if (_onErr) _onErr(err);
        };
        server.onclose = async () => {
            //clearInterval(updateInterval);
            await server.close();
            console.log("SSE connection closed.");
        };
    });

    app.post("/message", async (req, res) => {
        console.log("--> Received message (post)");
        if (transport?.handlePostMessage) {
            await transport.handlePostMessage(req, res);
        } else {
            console.error("transport.handlePostMessage UNDEFINED!");
        }
        console.log("<--", res.statusCode, res.statusMessage);
    });

    app.listen(PORT, () => {
        console.log(`Server is running on port ${PORT}`);
    });
}

runMCPServer().catch(console.error);

this is the cursor's error

[imikemiller]

If you have declared capabilities you have to implement the expected list and call endpoints

[felixweinberger]

Hi @wyyufeng thanks for submitting this issue - apologies for the time it took to get back to you, but given significant time has passed is this still affecting you?