Merge pull request #363 from modelcontextprotocol/ihrpr/stateless-example-fix

Streamable Http - fix examples for streamable HTTP

README.md

@@ -309,35 +309,72 @@ app.listen(3000);
 For simpler use cases where session management isn't needed:
 
 ```typescript
-import express from "express";
-import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
-import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
-
-const server = new McpServer({
-  name: "stateless-server",
-  version: "1.0.0"
-});
-
-// ... set up server resources, tools, and prompts ...
-
 const app = express();
 app.use(express.json());
 
-// Handle all MCP requests (GET, POST, DELETE) at a single endpoint
-app.all('/mcp', async (req, res) => {
-  // Disable session tracking by setting sessionIdGenerator to undefined  
-  const transport = new StreamableHTTPServerTransport({
-    sessionIdGenerator: undefined,
-    req,
-    res
-  });
-  
-  // Connect to server and handle the request
-  await server.connect(transport);
-  await transport.handleRequest(req, res);
+const transport: StreamableHTTPServerTransport = new StreamableHTTPServerTransport({
+  sessionIdGenerator: undefined, // set to undefined for stateless servers
+});
+
+// Setup routes for the server
+const setupServer = async () => {
+  await server.connect(transport);
+};
+
+app.post('/mcp', async (req: Request, res: Response) => {
+  console.log('Received MCP request:', req.body);
+  try {
+      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,
+      });
+    }
+  }
+});
+
+app.get('/mcp', async (req: Request, res: Response) => {
+  console.log('Received GET MCP request');
+  res.writeHead(405).end(JSON.stringify({
+    jsonrpc: "2.0",
+    error: {
+      code: -32000,
+      message: "Method not allowed."
+    },
+    id: null
+  }));
+});
+
+app.delete('/mcp', async (req: Request, res: Response) => {
+  console.log('Received DELETE MCP request');
+  res.writeHead(405).end(JSON.stringify({
+    jsonrpc: "2.0",
+    error: {
+      code: -32000,
+      message: "Method not allowed."
+    },
+    id: null
+  }));
+});
+
+// Start the server
+const PORT = 3000;
+setupServer().then(() => {
+  app.listen(PORT, () => {
+    console.log(`MCP Streamable HTTP Server listening on port ${PORT}`);
+  });
+}).catch(error => {
+  console.error('Failed to set up the server:', error);
+  process.exit(1);
 });
 
-app.listen(3000);
 ```
 
 This stateless approach is useful for:

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@modelcontextprotocol/sdk",
-  "version": "1.10.0",
+  "version": "1.10.1",
   "description": "Model Context Protocol implementation for TypeScript",
   "license": "MIT",
   "author": "Anthropic, PBC (https://anthropic.com)",

src/examples/server/simpleStatelessStreamableHttp.ts

@@ -0,0 +1,172 @@
+import express, { Request, Response } from 'express';
+import { McpServer } from '../../server/mcp.js';
+import { StreamableHTTPServerTransport } from '../../server/streamableHttp.js';
+import { z } from 'zod';
+import { CallToolResult, GetPromptResult, ReadResourceResult } from '../../types.js';
+
+// Create an MCP server with implementation details
+const server = new McpServer({
+  name: 'stateless-streamable-http-server',
+  version: '1.0.0',
+}, { capabilities: { logging: {} } });
+
+// Register a simple prompt
+server.prompt(
+  'greeting-template',
+  'A simple greeting prompt template',
+  {
+    name: z.string().describe('Name to include in greeting'),
+  },
+  async ({ name }): Promise<GetPromptResult> => {
+    return {
+      messages: [
+        {
+          role: 'user',
+          content: {
+            type: 'text',
+            text: `Please greet ${name} in a friendly manner.`,
+          },
+        },
+      ],
+    };
+  }
+);
+
+// Register a tool specifically for testing resumability
+server.tool(
+  'start-notification-stream',
+  'Starts sending periodic notifications for testing resumability',
+  {
+    interval: z.number().describe('Interval in milliseconds between notifications').default(100),
+    count: z.number().describe('Number of notifications to send (0 for 100)').default(10),
+  },
+  async ({ interval, count }, { sendNotification }): Promise<CallToolResult> => {
+    const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));
+    let counter = 0;
+
+    while (count === 0 || counter < count) {
+      counter++;
+      try {
+        await sendNotification({
+          method: "notifications/message",
+          params: {
+            level: "info",
+            data: `Periodic notification #${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 a simple resource at a fixed URI
+server.resource(
+  'greeting-resource',
+  'https://example.com/greetings/default',
+  { mimeType: 'text/plain' },
+  async (): Promise<ReadResourceResult> => {
+    return {
+      contents: [
+        {
+          uri: 'https://example.com/greetings/default',
+          text: 'Hello, world!',
+        },
+      ],
+    };
+  }
+);
+
+const app = express();
+app.use(express.json());
+
+const transport: StreamableHTTPServerTransport = new StreamableHTTPServerTransport({
+  sessionIdGenerator: undefined,
+});
+
+// Setup routes for the server
+const setupServer = async () => {
+  await server.connect(transport);
+};
+
+app.post('/mcp', async (req: Request, res: Response) => {
+  console.log('Received MCP request:', req.body);
+  try {
+      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,
+      });
+    }
+  }
+});
+
+app.get('/mcp', async (req: Request, res: Response) => {
+  console.log('Received GET MCP request');
+  res.writeHead(405).end(JSON.stringify({
+    jsonrpc: "2.0",
+    error: {
+      code: -32000,
+      message: "Method not allowed."
+    },
+    id: null
+  }));
+});
+
+app.delete('/mcp', async (req: Request, res: Response) => {
+  console.log('Received DELETE MCP request');
+  res.writeHead(405).end(JSON.stringify({
+    jsonrpc: "2.0",
+    error: {
+      code: -32000,
+      message: "Method not allowed."
+    },
+    id: null
+  }));
+});
+
+// Start the server
+const PORT = 3000;
+setupServer().then(() => {
+  app.listen(PORT, () => {
+    console.log(`MCP Streamable HTTP Server listening on port ${PORT}`);
+  });
+}).catch(error => {
+  console.error('Failed to set up the server:', error);
+  process.exit(1);
+});
+
+// Handle server shutdown
+process.on('SIGINT', async () => {
+  console.log('Shutting down server...');
+    try {
+      console.log(`Closing transport`);
+      await transport.close();
+    } catch (error) {
+      console.error(`Error closing transport:`, error);
+    }
+  
+  await server.close();
+  console.log('Server shutdown complete');
+  process.exit(0);
+});

src/integration-tests/stateManagementStreamableHttp.test.ts

@@ -109,6 +109,44 @@ describe('Streamable HTTP Transport Session Management', () => {
       server.close();
     });
 
+    it('should support multiple client connections', async () => {
+      // Create and connect a client
+      const client1 = new Client({
+        name: 'test-client',
+        version: '1.0.0'
+      });
+
+      const transport1 = new StreamableHTTPClientTransport(baseUrl);
+      await client1.connect(transport1);
+
+      // Verify that no session ID was set
+      expect(transport1.sessionId).toBeUndefined();
+
+      // List available tools
+      await client1.request({
+        method: 'tools/list',
+        params: {}
+      }, ListToolsResultSchema);
+
+      const client2 = new Client({
+        name: 'test-client',
+        version: '1.0.0'
+      });
+
+      const transport2 = new StreamableHTTPClientTransport(baseUrl);
+      await client2.connect(transport2);
+
+      // Verify that no session ID was set
+      expect(transport2.sessionId).toBeUndefined();
+
+      // List available tools
+      await client2.request({
+        method: 'tools/list',
+        params: {}
+      }, ListToolsResultSchema);
+
+      
+    });
     it('should operate without session management', async () => {
       // Create and connect a client
       const client = new Client({

src/server/streamableHttp.ts

@@ -343,7 +343,7 @@ export class StreamableHTTPServerTransport implements Transport {
       if (isInitializationRequest) {
         // If it's a server with session management and the session ID is already set we should reject the request
         // to avoid re-initialization.
-        if (this._initialized) {
+        if (this._initialized && this.sessionId !== undefined) {
           res.writeHead(400).end(JSON.stringify({
             jsonrpc: "2.0",
             error: {