diff --git a/src/examples/server/sseAndStreamableHttpCompatibleServer.ts b/src/examples/server/sseAndStreamableHttpCompatibleServer.ts new file mode 100644 index 00000000..5a79a4e5 --- /dev/null +++ b/src/examples/server/sseAndStreamableHttpCompatibleServer.ts @@ -0,0 +1,316 @@ +import express, { Request, Response } from 'express'; +import { randomUUID } from "node:crypto"; +import { McpServer } from '../../server/mcp.js'; +import { EventStore, StreamableHTTPServerTransport } from '../../server/streamableHttp.js'; +import { SSEServerTransport } from '../../server/sse.js'; +import { z } from 'zod'; +import { CallToolResult, isInitializeRequest, JSONRPCMessage } from '../../types.js'; + +/** + * This example server demonstrates backwards compatibility with both: + * 1. The deprecated HTTP+SSE transport (protocol version 2024-11-05) + * 2. The Streamable HTTP transport (protocol version 2025-03-26) + * + * It maintains a single MCP server instance but exposes two transport options: + * - /mcp: The new Streamable HTTP endpoint (supports GET/POST/DELETE) + * - /sse: The deprecated SSE endpoint for older clients (GET to establish stream) + * - /request: The deprecated POST endpoint for older clients (POST to send messages) + */ + +// Simple in-memory event store for resumability +class InMemoryEventStore implements EventStore { + private events: Map = new Map(); + + /** + * Generates a unique event ID for a given stream ID + */ + private generateEventId(streamId: string): string { + return `${streamId}_${Date.now()}_${Math.random().toString(36).substring(2, 10)}`; + } + + private getStreamIdFromEventId(eventId: string): string { + const parts = eventId.split('_'); + return parts.length > 0 ? parts[0] : ''; + } + + /** + * Stores an event with a generated event ID + * Implements EventStore.storeEvent + */ + async storeEvent(streamId: string, message: JSONRPCMessage): Promise { + const eventId = this.generateEventId(streamId); + console.log(`Storing event ${eventId} for stream ${streamId}`); + this.events.set(eventId, { streamId, message }); + return eventId; + } + + /** + * Replays events that occurred after a specific event ID + * Implements EventStore.replayEventsAfter + */ + async replayEventsAfter(lastEventId: string, + { send }: { send: (eventId: string, message: JSONRPCMessage) => Promise } + ): Promise { + if (!lastEventId || !this.events.has(lastEventId)) { + console.log(`No events found for lastEventId: ${lastEventId}`); + return ''; + } + + const streamId = this.getStreamIdFromEventId(lastEventId); + if (!streamId) { + console.log(`Could not extract streamId from lastEventId: ${lastEventId}`); + return ''; + } + + let foundLastEvent = false; + let eventCount = 0; + + // Sort events by eventId for chronological ordering + const sortedEvents = [...this.events.entries()].sort((a, b) => a[0].localeCompare(b[0])); + + for (const [eventId, { streamId: eventStreamId, message }] of sortedEvents) { + // Only include events from the same stream + if (eventStreamId !== streamId) { + continue; + } + + // Start sending events after we find the lastEventId + if (eventId === lastEventId) { + foundLastEvent = true; + continue; + } + + if (foundLastEvent) { + await send(eventId, message); + eventCount++; + } + } + + console.log(`Replayed ${eventCount} events after ${lastEventId} for stream ${streamId}`); + return streamId; + } +} + +// Create a shared MCP server instance +const server = new McpServer({ + name: 'backwards-compatible-server', + version: '1.0.0', +}, { capabilities: { logging: {} } }); + +// Register a simple tool that sends notifications over time +server.tool( + 'start-notification-stream', + 'Starts sending periodic notifications for testing resumability', + { + interval: z.number().describe('Interval in milliseconds between notifications').default(100), + count: z.number().describe('Number of notifications to send (0 for 100)').default(50), + }, + async ({ interval, count }, { sendNotification }): Promise => { + const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms)); + let counter = 0; + + while (count === 0 || counter < count) { + counter++; + try { + await sendNotification({ + method: "notifications/message", + params: { + level: "info", + data: `Periodic notification #${counter} at ${new Date().toISOString()}` + } + }); + } + catch (error) { + console.error("Error sending notification:", error); + } + // Wait for the specified interval + await sleep(interval); + } + + return { + content: [ + { + type: 'text', + text: `Started sending periodic notifications every ${interval}ms`, + } + ], + }; + } +); + +// Create Express application +const app = express(); +app.use(express.json()); + +// Store transports by session ID +const transports: Record = {}; + +//============================================================================= +// STREAMABLE HTTP TRANSPORT (PROTOCOL VERSION 2025-03-26) +//============================================================================= + +// Handle all MCP Streamable HTTP requests (GET, POST, DELETE) on a single endpoint +app.all('/mcp', async (req: Request, res: Response) => { + console.log(`Received ${req.method} request to /mcp`); + + try { + // Check for existing session ID + const sessionId = req.headers['mcp-session-id'] as string | undefined; + let transport: StreamableHTTPServerTransport; + + if (sessionId && transports[sessionId]) { + // Check if the transport is of the correct type + const existingTransport = transports[sessionId]; + if (existingTransport instanceof StreamableHTTPServerTransport) { + // Reuse existing transport + transport = existingTransport; + } else { + // Transport exists but is not a StreamableHTTPServerTransport (could be SSEServerTransport) + res.status(400).json({ + jsonrpc: '2.0', + error: { + code: -32000, + message: 'Bad Request: Session exists but uses a different transport protocol', + }, + id: null, + }); + return; + } + } else if (!sessionId && req.method === 'POST' && isInitializeRequest(req.body)) { + const eventStore = new InMemoryEventStore(); + transport = new StreamableHTTPServerTransport({ + sessionIdGenerator: () => randomUUID(), + eventStore, // Enable resumability + onsessioninitialized: (sessionId) => { + // Store the transport by session ID when session is initialized + console.log(`StreamableHTTP session initialized with ID: ${sessionId}`); + transports[sessionId] = transport; + } + }); + + // Set up onclose handler to clean up transport when closed + transport.onclose = () => { + const sid = transport.sessionId; + if (sid && transports[sid]) { + console.log(`Transport closed for session ${sid}, removing from transports map`); + delete transports[sid]; + } + }; + + // Connect the transport to the MCP server + await server.connect(transport); + } else { + // Invalid request - no session ID or not initialization request + res.status(400).json({ + jsonrpc: '2.0', + error: { + code: -32000, + message: 'Bad Request: No valid session ID provided', + }, + id: null, + }); + return; + } + + // Handle the request with the transport + await transport.handleRequest(req, res, req.body); + } catch (error) { + console.error('Error handling MCP request:', error); + if (!res.headersSent) { + res.status(500).json({ + jsonrpc: '2.0', + error: { + code: -32603, + message: 'Internal server error', + }, + id: null, + }); + } + } +}); + +//============================================================================= +// DEPRECATED HTTP+SSE TRANSPORT (PROTOCOL VERSION 2024-11-05) +//============================================================================= + +app.get('/sse', async (req: Request, res: Response) => { + console.log('Received GET request to /sse (deprecated SSE transport)'); + const transport = new SSEServerTransport('/messages', res); + transports[transport.sessionId] = transport; + res.on("close", () => { + delete transports[transport.sessionId]; + }); + await server.connect(transport); +}); + +app.post("/messages", async (req: Request, res: Response) => { + const sessionId = req.query.sessionId as string; + let transport: SSEServerTransport; + const existingTransport = transports[sessionId]; + if (existingTransport instanceof SSEServerTransport) { + // Reuse existing transport + transport = existingTransport; + } else { + // Transport exists but is not a SSEServerTransport (could be StreamableHTTPServerTransport) + res.status(400).json({ + jsonrpc: '2.0', + error: { + code: -32000, + message: 'Bad Request: Session exists but uses a different transport protocol', + }, + id: null, + }); + return; + } + if (transport) { + await transport.handlePostMessage(req, res); + } else { + res.status(400).send('No transport found for sessionId'); + } +}); + + +// Start the server +const PORT = 3000; +app.listen(PORT, () => { + console.log(`Backwards compatible MCP server listening on port ${PORT}`); + console.log(` +============================================== +SUPPORTED TRANSPORT OPTIONS: + +1. Streamable Http(Protocol version: 2025-03-26) + Endpoint: /mcp + Methods: GET, POST, DELETE + Usage: + - Initialize with POST to /mcp + - Establish SSE stream with GET to /mcp + - Send requests with POST to /mcp + - Terminate session with DELETE to /mcp + +2. Http + SSE (Protocol version: 2024-11-05) + Endpoints: /sse (GET) and /request (POST) + Usage: + - Establish SSE stream with GET to /sse + - Send requests with POST to /message?sessionId= +============================================== +`); +}); + +// Handle server shutdown +process.on('SIGINT', async () => { + console.log('Shutting down server...'); + + // Close all active transports to properly clean up resources + for (const sessionId in transports) { + try { + console.log(`Closing transport for session ${sessionId}`); + await transports[sessionId].close(); + delete transports[sessionId]; + } catch (error) { + console.error(`Error closing transport for session ${sessionId}:`, error); + } + } + await server.close(); + console.log('Server shutdown complete'); + process.exit(0); +}); \ No newline at end of file