Lorem Ipsum MCP Server

import { Server } from "@modelcontextprotocol/sdk/server/index.js"; import { EventStore, StreamableHTTPServerTransport, } from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js"; import http from "http"; import { randomUUID } from "node:crypto"; import { InMemoryEventStore } from "./InMemoryEventStore.js"; export type SSEServer = { close: () => Promise<void>; }; type ServerLike = { close: Server["close"]; connect: Server["connect"]; }; export const startHTTPStreamServer = async <T extends ServerLike>({ createServer, endpoint, eventStore, onClose, onConnect, onUnhandledRequest, port, }: { createServer: (request: http.IncomingMessage) => Promise<T>; endpoint: string; eventStore?: EventStore; onClose?: (server: T) => void; onConnect?: (server: T) => void; onUnhandledRequest?: ( req: http.IncomingMessage, res: http.ServerResponse, ) => Promise<void>; port: number; }): Promise<SSEServer> => { const activeTransports: Record< string, { server: T; transport: StreamableHTTPServerTransport; } > = {}; /** * @author https://dev.classmethod.jp/articles/mcp-sse/ */ const httpServer = http.createServer(async (req, res) => { if (req.headers.origin) { try { const origin = new URL(req.headers.origin); res.setHeader("Access-Control-Allow-Origin", origin.origin); res.setHeader("Access-Control-Allow-Credentials", "true"); res.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS"); res.setHeader("Access-Control-Allow-Headers", "*"); } catch (error) { console.error("Error parsing origin:", error); } } if (req.method === "OPTIONS") { res.writeHead(204); res.end(); return; } if (req.method === "GET" && req.url === `/ping`) { res.writeHead(200).end("pong"); return; } if ( req.method === "POST" && new URL(req.url!, "http://localhost").pathname === endpoint ) { try { const sessionId = Array.isArray(req.headers["mcp-session-id"]) ? req.headers["mcp-session-id"][0] : req.headers["mcp-session-id"]; let transport: StreamableHTTPServerTransport; let server: T; const body = await getBody(req); if (sessionId && activeTransports[sessionId]) { transport = activeTransports[sessionId].transport; server = activeTransports[sessionId].server; } else if (!sessionId && isInitializeRequest(body)) { // Create a new transport for the session transport = new StreamableHTTPServerTransport({ eventStore: eventStore || new InMemoryEventStore(), onsessioninitialized: (_sessionId) => { // add only when the id Sesison id is generated activeTransports[_sessionId] = { server, transport, }; }, sessionIdGenerator: randomUUID, }); // Handle the server close event transport.onclose = async () => { const sid = transport.sessionId; if (sid && activeTransports[sid]) { onClose?.(server); try { await server.close(); } catch (error) { console.error("Error closing server:", error); } delete activeTransports[sid]; } }; // Create the server try { server = await createServer(req); } catch (error) { if (error instanceof Response) { res.writeHead(error.status).end(error.statusText); return; } res.writeHead(500).end("Error creating server"); return; } server.connect(transport); onConnect?.(server); await transport.handleRequest(req, res, body); return; } else { // Error if the server is not created but the request is not an initialize request res.setHeader("Content-Type", "application/json"); res.writeHead(400).end( JSON.stringify({ error: { code: -32000, message: "Bad Request: No valid session ID provided", }, id: null, jsonrpc: "2.0", }), ); return; } // Handle ther request if the server is already created await transport.handleRequest(req, res, body); } catch (error) { console.error("Error handling request:", error); res.setHeader("Content-Type", "application/json"); res.writeHead(500).end( JSON.stringify({ error: { code: -32603, message: "Internal Server Error" }, id: null, jsonrpc: "2.0", }), ); } return; } if ( req.method === "GET" && new URL(req.url!, "http://localhost").pathname === endpoint ) { const sessionId = req.headers["mcp-session-id"] as string | undefined; const activeTransport: | { server: T; transport: StreamableHTTPServerTransport; } | undefined = sessionId ? activeTransports[sessionId] : undefined; if (!sessionId) { res.writeHead(400).end("No sessionId"); return; } if (!activeTransport) { res.writeHead(400).end("No active transport"); return; } const lastEventId = req.headers["last-event-id"] as string | undefined; if (lastEventId) { console.log(`Client reconnecting with Last-Event-ID: ${lastEventId}`); } else { console.log(`Establishing new SSE stream for session ${sessionId}`); } await activeTransport.transport.handleRequest(req, res); return; } if ( req.method === "DELETE" && new URL(req.url!, "http://localhost").pathname === endpoint ) { console.log("received delete request"); const sessionId = req.headers["mcp-session-id"] as string | undefined; if (!sessionId) { res.writeHead(400).end("Invalid or missing sessionId"); return; } console.log("received delete request for session", sessionId); const { server, transport } = activeTransports[sessionId]; if (!transport) { res.writeHead(400).end("No active transport"); return; } try { await transport.handleRequest(req, res); onClose?.(server); } catch (error) { console.error("Error handling delete request:", error); res.writeHead(500).end("Error handling delete request"); } return; } if (onUnhandledRequest) { await onUnhandledRequest(req, res); } else { res.writeHead(404).end(); } }); await new Promise((resolve) => { httpServer.listen(port, "::", () => { resolve(undefined); }); }); return { close: async () => { for (const transport of Object.values(activeTransports)) { await transport.transport.close(); } return new Promise((resolve, reject) => { httpServer.close((error) => { if (error) { reject(error); return; } resolve(); }); }); }, }; }; function getBody(request: http.IncomingMessage) { return new Promise((resolve) => { const bodyParts: Buffer[] = []; let body: string; request .on("data", (chunk) => { bodyParts.push(chunk); }) .on("end", () => { body = Buffer.concat(bodyParts).toString(); resolve(JSON.parse(body)); }); }); }