example of sse server

src/examples/server/simpleSseServer.ts

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+import express, { Request, Response } from 'express';
+import { randomUUID } from "node:crypto";
+import { McpServer } from '../../server/mcp.js';
+import { SSEServerTransport } from '../../server/sse.js';
+import { z } from 'zod';
+import { CallToolResult } from '../../types.js';
+
+/**
+ * This example server demonstrates the deprecated HTTP+SSE transport 
+ * (protocol version 2024-11-05). It mainly used for testing backward compatible clients.
+ * 
+ * The server exposes two endpoints:
+ * - /sse: For establishing the SSE stream (GET)
+ * - /messages: For receiving client messages (POST)
+ * 
+ */
+
+// Create an MCP server instance
+const server = new McpServer({
+  name: 'simple-sse-server',
+  version: '1.0.0',
+}, { capabilities: { logging: {} } });
+
+server.tool(
+  'start-notification-stream',
+  'Starts sending periodic notifications',
+  {
+    interval: z.number().describe('Interval in milliseconds between notifications').default(1000),
+    count: z.number().describe('Number of notifications to send').default(10),
+  },
+  async ({ interval, count }, { sendNotification }): Promise<CallToolResult> => {
+    const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));
+    let counter = 0;
+
+    // Send the initial notification
+    await sendNotification({
+      method: "notifications/message",
+      params: {
+        level: "info",
+        data: `Starting notification stream with ${count} messages every ${interval}ms`
+      }
+    });
+
+    // Send periodic notifications
+    while (counter < count) {
+      counter++;
+      await sleep(interval);
+
+      try {
+        await sendNotification({
+          method: "notifications/message",
+          params: {
+            level: "info",
+            data: `Notification #${counter} at ${new Date().toISOString()}`
+          }
+        });
+      }
+      catch (error) {
+        console.error("Error sending notification:", error);
+      }
+    }
+
+    return {
+      content: [
+        {
+          type: 'text',
+          text: `Completed sending ${count} notifications every ${interval}ms`,
+        }
+      ],
+    };
+  }
+);
+
+const app = express();
+app.use(express.json());
+
+// Store transports by session ID
+const transports: Record<string, SSEServerTransport> = {};
+
+// SSE endpoint for establishing the stream
+app.get('/sse', async (req: Request, res: Response) => {
+  console.log('Received GET request to /sse (establishing SSE stream)');
+
+  try {
+    // Create a new SSE transport for the client
+    // The endpoint for POST messages is '/messages'
+    const transport = new SSEServerTransport('/messages', res);
+
+    // Store the transport by session ID
+    const sessionId = transport.sessionId;
+    transports[sessionId] = transport;
+
+    // Set up onclose handler to clean up transport when closed
+    transport.onclose = () => {
+      console.log(`SSE transport closed for session ${sessionId}`);
+      delete transports[sessionId];
+    };
+
+    // Connect the transport to the MCP server
+    await server.connect(transport);
+
+    // Start the SSE transport to begin streaming
+    // This sends an initial 'endpoint' event with the session ID in the URL
+    await transport.start();
+
+    console.log(`Established SSE stream with session ID: ${sessionId}`);
+  } catch (error) {
+    console.error('Error establishing SSE stream:', error);
+    if (!res.headersSent) {
+      res.status(500).send('Error establishing SSE stream');
+    }
+  }
+});
+
+// Messages endpoint for receiving client JSON-RPC requests
+app.post('/messages', async (req: Request, res: Response) => {
+  console.log('Received POST request to /messages');
+
+  // Extract session ID from URL query parameter
+  // In the SSE protocol, this is added by the client based on the endpoint event
+  const sessionId = req.query.sessionId as string | undefined;
+
+  if (!sessionId) {
+    console.error('No session ID provided in request URL');
+    res.status(400).send('Missing sessionId parameter');
+    return;
+  }
+
+  const transport = transports[sessionId];
+  if (!transport) {
+    console.error(`No active transport found for session ID: ${sessionId}`);
+    res.status(404).send('Session not found');
+    return;
+  }
+
+  try {
+    // Handle the POST message with the transport
+    await transport.handlePostMessage(req, res, req.body);
+  } catch (error) {
+    console.error('Error handling request:', error);
+    if (!res.headersSent) {
+      res.status(500).send('Error handling request');
+    }
+  }
+});
+
+// Start the server
+const PORT = 3000;
+app.listen(PORT, () => {
+  console.log(`Simple SSE Server (deprecated protocol version 2024-11-05) listening on port ${PORT}`);
+});
+
+// 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);
+});