mcp-hello-world/build/http.js

A simple Hello World MCP server

#!/usr/bin/env node
import express from "express";
import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
import { createServer } from "./server.js";
async function main() {
    // Create the server
    const server = createServer();
    // Create Express app
    const app = express();
    const port = process.env.PORT || 3000;
    // Server-side connections
    const connections = new Map();
    // Handle SSE connections
    app.get("/sse", async (req, res) => {
        // Generate a unique connection ID (UUID format)
        const sessionId = req.query.sessionId ||
            `${Math.random().toString(36).substring(2, 15)}-${Date.now().toString(36)}`;
        try {
            // Create a new SSE transport
            const transport = new SSEServerTransport(`/messages?sessionId=${sessionId}`, res);
            connections.set(sessionId, transport);
            // Connect the server to this transport
            await server.connect(transport);
        }
        catch (error) {
            console.error('Error establishing SSE connection:', error);
            // If headers already sent due to transport.start(), don't try to set them again
            if (!res.headersSent) {
                res.status(500).end(`Server error: ${error.message || 'Unknown error'}`);
            }
        }
        // Handle client disconnect
        req.on("close", () => {
            if (connections.has(sessionId)) {
                connections.delete(sessionId);
                console.error(`Client ${sessionId} disconnected`);
            }
        });
    });
    // Handle messages from client
    app.post("/messages", express.json(), async (req, res) => {
        try {
            // Extract sessionId from query parameters
            const sessionId = req.query.sessionId;
            console.log(`Received message for session ${sessionId}, body:`, req.body);
            if (!sessionId || !connections.has(sessionId)) {
                // If no sessionId or connection not found, try the first connection
                if (connections.size === 0) {
                    return res.status(400).json({ error: "No active connections" });
                }
                console.log('Using first available connection');
                const transport = connections.values().next().value;
                await transport.handlePostMessage(req, res, req.body);
            }
            else {
                // Use the specific connection for this session
                console.log(`Using connection for session ${sessionId}`);
                const transport = connections.get(sessionId);
                await transport.handlePostMessage(req, res, req.body);
            }
        }
        catch (error) {
            console.error('Error handling message:', error);
            if (!res.headersSent) {
                res.status(500).json({ error: `Internal server error: ${error.message || 'Unknown error'}` });
            }
        }
    });
    // Debug: log available methods
    console.error('Available methods in the MCP server:');
    console.error('Server object keys:', Object.keys(server));
    console.error('Server constructor:', server.constructor.name);
    // Start the server
    app.listen(port, () => {
        console.error(`Hello World MCP Server running on http://localhost:${port}`);
        console.error(`- Connect to /sse for server-sent events`);
        console.error(`- Send messages to /messages endpoint`);
    });
}
main().catch((error) => {
    console.error("Fatal error in main():", error);
    process.exit(1);
});