252 lines
9.5 KiB
JavaScript
252 lines
9.5 KiB
JavaScript
import express from 'express';
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import { randomUUID } from 'node:crypto';
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import { z } from 'zod';
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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 { isInitializeRequest } from '../../types.js';
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import { InMemoryEventStore } from '../shared/inMemoryEventStore.js';
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// Create an MCP server with implementation details
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const getServer = () => {
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const server = new McpServer({
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name: 'simple-streamable-http-server',
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version: '1.0.0',
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}, { capabilities: { logging: {} } });
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// Register a simple tool that returns a greeting
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server.tool('greet', 'A simple greeting tool', {
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name: z.string().describe('Name to greet'),
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}, async ({ name }) => {
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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: `Hello, ${name}!`,
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},
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],
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};
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});
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// Register a tool that sends multiple greetings with notifications (with annotations)
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server.tool('multi-greet', 'A tool that sends different greetings with delays between them', {
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name: z.string().describe('Name to greet'),
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}, {
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title: 'Multiple Greeting Tool',
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readOnlyHint: true,
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openWorldHint: false
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}, async ({ name }, { sendNotification }) => {
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const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));
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await sendNotification({
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method: "notifications/message",
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params: { level: "debug", data: `Starting multi-greet for ${name}` }
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});
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await sleep(1000); // Wait 1 second before first greeting
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await sendNotification({
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method: "notifications/message",
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params: { level: "info", data: `Sending first greeting to ${name}` }
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});
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await sleep(1000); // Wait another second before second greeting
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await sendNotification({
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method: "notifications/message",
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params: { level: "info", data: `Sending second greeting to ${name}` }
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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: `Good morning, ${name}!`,
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}
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],
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};
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});
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// Register a simple prompt
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server.prompt('greeting-template', 'A simple greeting prompt template', {
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name: z.string().describe('Name to include in greeting'),
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}, async ({ name }) => {
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return {
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messages: [
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{
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role: 'user',
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content: {
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type: 'text',
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text: `Please greet ${name} in a friendly manner.`,
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},
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},
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],
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};
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});
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// Register a tool specifically for testing resumability
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server.tool('start-notification-stream', 'Starts sending periodic notifications for testing resumability', {
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interval: z.number().describe('Interval in milliseconds between notifications').default(100),
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count: z.number().describe('Number of notifications to send (0 for 100)').default(50),
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}, async ({ interval, count }, { sendNotification }) => {
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const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));
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let counter = 0;
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while (count === 0 || counter < count) {
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counter++;
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try {
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await sendNotification({
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method: "notifications/message",
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params: {
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level: "info",
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data: `Periodic notification #${counter} at ${new Date().toISOString()}`
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}
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});
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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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// Create a simple resource at a fixed URI
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server.resource('greeting-resource', 'https://example.com/greetings/default', { mimeType: 'text/plain' }, async () => {
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return {
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contents: [
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{
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uri: 'https://example.com/greetings/default',
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text: 'Hello, world!',
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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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const app = express();
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app.use(express.json());
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// Map to store transports by session ID
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const transports = {};
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app.post('/mcp', async (req, res) => {
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console.log('Received MCP request:', req.body);
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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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let transport;
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if (sessionId && transports[sessionId]) {
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// Reuse existing transport
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transport = transports[sessionId];
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}
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else if (!sessionId && isInitializeRequest(req.body)) {
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// New initialization request
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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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// This avoids race conditions where requests might come in before the session is stored
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console.log(`Session initialized with ID: ${sessionId}`);
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transports[sessionId] = transport;
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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 && transports[sid]) {
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console.log(`Transport closed for session ${sid}, removing from transports map`);
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delete transports[sid];
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}
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};
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// Connect the transport to the MCP server BEFORE handling the request
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// so responses can flow back through the same transport
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const server = getServer();
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await server.connect(transport);
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await transport.handleRequest(req, res, req.body);
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return; // Already handled
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}
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else {
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// Invalid request - no session ID or not 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 existing transport - no need to reconnect
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// The existing transport is already connected to the server
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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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// Handle GET requests for SSE streams (using built-in support from StreamableHTTP)
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app.get('/mcp', async (req, res) => {
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const sessionId = req.headers['mcp-session-id'];
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if (!sessionId || !transports[sessionId]) {
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res.status(400).send('Invalid or missing session ID');
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return;
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}
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// Check for Last-Event-ID header for resumability
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const lastEventId = req.headers['last-event-id'];
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if (lastEventId) {
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console.log(`Client reconnecting with Last-Event-ID: ${lastEventId}`);
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}
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else {
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console.log(`Establishing new SSE stream for session ${sessionId}`);
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}
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const transport = transports[sessionId];
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await transport.handleRequest(req, res);
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});
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// Handle DELETE requests for session termination (according to MCP spec)
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app.delete('/mcp', async (req, res) => {
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const sessionId = req.headers['mcp-session-id'];
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if (!sessionId || !transports[sessionId]) {
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res.status(400).send('Invalid or missing session ID');
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return;
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}
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console.log(`Received session termination request for session ${sessionId}`);
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try {
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const transport = transports[sessionId];
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await transport.handleRequest(req, res);
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}
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catch (error) {
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console.error('Error handling session termination:', error);
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if (!res.headersSent) {
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res.status(500).send('Error processing session termination');
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}
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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, () => {
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console.log(`MCP Streamable HTTP Server listening on port ${PORT}`);
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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 in transports) {
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try {
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console.log(`Closing transport for session ${sessionId}`);
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await transports[sessionId].close();
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delete transports[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=simpleStreamableHttp.js.map
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