269 lines
11 KiB
Plaintext
269 lines
11 KiB
Plaintext
import { randomUUID } from 'node:crypto';
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import { McpServer } from '../../server/mcp.js';
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import { StreamableHTTPServerTransport } from '../../server/streamableHttp.js';
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import { SSEServerTransport } from '../../server/sse.js';
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import * as z from 'zod/v4';
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import { isInitializeRequest } from '../../types.js';
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import { InMemoryEventStore } from '../shared/inMemoryEventStore.js';
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import { createMcpExpressApp } from '../../server/express.js';
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/**
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* This example server demonstrates backwards compatibility with both:
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* 1. The deprecated HTTP+SSE transport (protocol version 2024-11-05)
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* 2. The Streamable HTTP transport (protocol version 2025-11-25)
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*
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* It maintains a single MCP server instance but exposes two transport options:
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* - /mcp: The new Streamable HTTP endpoint (supports GET/POST/DELETE)
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* - /sse: The deprecated SSE endpoint for older clients (GET to establish stream)
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* - /messages: The deprecated POST endpoint for older clients (POST to send messages)
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*/
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const getServer = () => {
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const server = new McpServer({
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name: 'backwards-compatible-server',
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version: '1.0.0'
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}, { capabilities: { logging: {} } });
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// Register a simple tool that sends notifications over time
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server.registerTool('start-notification-stream', {
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description: 'Starts sending periodic notifications for testing resumability',
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inputSchema: {
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interval: z.number().describe('Interval in milliseconds between notifications').default(100),
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count: z.number().describe('Number of notifications to send (0 for 100)').default(50)
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}
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}, async ({ interval, count }, extra) => {
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const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));
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let counter = 0;
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while (count === 0 || counter < count) {
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counter++;
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try {
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await server.sendLoggingMessage({
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level: 'info',
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data: `Periodic notification #${counter} at ${new Date().toISOString()}`
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}, extra.sessionId);
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}
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catch (error) {
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console.error('Error sending notification:', error);
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}
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// Wait for the specified interval
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await sleep(interval);
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}
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return {
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content: [
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{
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type: 'text',
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text: `Started sending periodic notifications every ${interval}ms`
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}
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]
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};
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});
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return server;
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};
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// Create Express application
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const app = createMcpExpressApp();
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// Close sessions that have been idle for IDLE_MS, and keep at most MAX_SESSIONS open
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const IDLE_MS = 30 * 60000;
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const MAX_SESSIONS = 1000;
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const sessions = new Map();
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// Count open responses so a long-running request or a listening SSE stream is not treated as idle
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const trackResponse = (session, res) => {
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if (!res.socket || res.destroyed)
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return;
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session.open++;
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res.on('close', () => {
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session.open--;
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session.lastActive = Date.now();
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});
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};
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// Close sessions with nothing open and no activity for IDLE_MS
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setInterval(() => {
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const cutoff = Date.now() - IDLE_MS;
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for (const { transport, open, lastActive } of sessions.values()) {
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if (open === 0 && lastActive < cutoff)
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transport.close().catch(console.error);
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}
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}, 60000).unref();
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//=============================================================================
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// STREAMABLE HTTP TRANSPORT (PROTOCOL VERSION 2025-11-25)
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//=============================================================================
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// Handle all MCP Streamable HTTP requests (GET, POST, DELETE) on a single endpoint
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app.all('/mcp', async (req, res) => {
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console.log(`Received ${req.method} request to /mcp`);
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try {
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// Check for existing session ID
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const sessionId = req.headers['mcp-session-id'];
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const session = sessionId ? sessions.get(sessionId) : undefined;
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let transport;
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if (session) {
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// Check if the transport is of the correct type
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if (session.transport instanceof StreamableHTTPServerTransport) {
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// Reuse existing transport
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transport = session.transport;
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trackResponse(session, res);
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}
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else {
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// Transport exists but is not a StreamableHTTPServerTransport (could be SSEServerTransport)
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res.status(400).json({
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jsonrpc: '2.0',
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error: {
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code: -32000,
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message: 'Bad Request: Session exists but uses a different transport protocol'
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},
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id: null
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});
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return;
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}
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}
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else if (!sessionId && req.method === 'POST' && isInitializeRequest(req.body)) {
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if (sessions.size >= MAX_SESSIONS) {
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res.status(503).json({ jsonrpc: '2.0', error: { code: -32000, message: 'Too many open sessions' }, id: null });
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return;
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}
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const eventStore = new InMemoryEventStore();
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transport = new StreamableHTTPServerTransport({
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sessionIdGenerator: () => randomUUID(),
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eventStore, // Enable resumability
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onsessioninitialized: sessionId => {
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// Store the transport by session ID when session is initialized
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console.log(`StreamableHTTP session initialized with ID: ${sessionId}`);
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sessions.set(sessionId, { transport, open: 0, lastActive: Date.now() });
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}
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});
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// Set up onclose handler to clean up transport when closed
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transport.onclose = () => {
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const sid = transport.sessionId;
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if (sid && sessions.has(sid)) {
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console.log(`Transport closed for session ${sid}, removing from sessions map`);
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sessions.delete(sid);
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}
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};
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// Connect the transport to the MCP server
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const server = getServer();
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await server.connect(transport);
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}
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else if (sessionId) {
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// Unknown or expired session ID - the client should start a new session
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res.status(404).json({ jsonrpc: '2.0', error: { code: -32001, message: 'Session not found' }, id: null });
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return;
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}
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else {
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// Invalid request - no session ID and not an initialization request
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res.status(400).json({
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jsonrpc: '2.0',
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error: {
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code: -32000,
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message: 'Bad Request: No valid session ID provided'
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},
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id: null
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});
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return;
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}
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// Handle the request with the transport
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await transport.handleRequest(req, res, req.body);
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}
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catch (error) {
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console.error('Error handling MCP request:', error);
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if (!res.headersSent) {
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res.status(500).json({
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jsonrpc: '2.0',
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error: {
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code: -32603,
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message: 'Internal server error'
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},
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id: null
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});
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}
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}
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});
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//=============================================================================
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// DEPRECATED HTTP+SSE TRANSPORT (PROTOCOL VERSION 2024-11-05)
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//=============================================================================
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app.get('/sse', async (req, res) => {
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console.log('Received GET request to /sse (deprecated SSE transport)');
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if (sessions.size >= MAX_SESSIONS) {
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res.status(503).send('Too many open sessions');
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return;
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}
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const transport = new SSEServerTransport('/messages', res);
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// An SSE session lasts as long as this response, which counts as open until it closes
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const session = { transport, open: 0, lastActive: Date.now() };
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sessions.set(transport.sessionId, session);
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trackResponse(session, res);
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// Set up onclose handler to clean up transport when closed
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transport.onclose = () => {
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sessions.delete(transport.sessionId);
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};
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const server = getServer();
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await server.connect(transport);
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});
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app.post('/messages', async (req, res) => {
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const sessionId = req.query.sessionId;
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let transport;
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const existingTransport = sessions.get(sessionId)?.transport;
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if (existingTransport instanceof SSEServerTransport) {
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// Reuse existing transport
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transport = existingTransport;
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}
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else {
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// Transport exists but is not a SSEServerTransport (could be StreamableHTTPServerTransport)
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res.status(400).json({
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jsonrpc: '2.0',
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error: {
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code: -32000,
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message: 'Bad Request: Session exists but uses a different transport protocol'
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},
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id: null
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});
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return;
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}
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if (transport) {
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await transport.handlePostMessage(req, res, req.body);
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}
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else {
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res.status(400).send('No transport found for sessionId');
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}
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});
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// Start the server
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const PORT = 3000;
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app.listen(PORT, error => {
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if (error) {
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console.error('Failed to start server:', error);
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process.exit(1);
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}
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console.log(`Backwards compatible MCP server listening on port ${PORT}`);
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console.log(`
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==============================================
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SUPPORTED TRANSPORT OPTIONS:
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1. Streamable Http(Protocol version: 2025-11-25)
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Endpoint: /mcp
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Methods: GET, POST, DELETE
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Usage:
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- Initialize with POST to /mcp
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- Establish SSE stream with GET to /mcp
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- Send requests with POST to /mcp
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- Terminate session with DELETE to /mcp
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2. Http + SSE (Protocol version: 2024-11-05)
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Endpoints: /sse (GET) and /messages (POST)
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Usage:
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- Establish SSE stream with GET to /sse
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- Send requests with POST to /messages?sessionId=<id>
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==============================================
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`);
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});
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// Handle server shutdown
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process.on('SIGINT', async () => {
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console.log('Shutting down server...');
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// Close all active transports to properly clean up resources
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for (const [sessionId, { transport }] of sessions) {
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try {
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console.log(`Closing transport for session ${sessionId}`);
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await transport.close();
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sessions.delete(sessionId);
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}
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catch (error) {
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console.error(`Error closing transport for session ${sessionId}:`, error);
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}
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}
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console.log('Server shutdown complete');
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process.exit(0);
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});
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//# sourceMappingURL=sseAndStreamableHttpCompatibleServer.js.map |