@modelcontextprotocol/sdk
Version:
Model Context Protocol implementation for TypeScript
253 lines (251 loc) • 10.2 kB
JavaScript
;
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__setModuleDefault(result, mod);
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Object.defineProperty(exports, "__esModule", { value: true });
const node_crypto_1 = require("node:crypto");
const mcp_js_1 = require("../../server/mcp.js");
const streamableHttp_js_1 = require("../../server/streamableHttp.js");
const sse_js_1 = require("../../server/sse.js");
const z = __importStar(require("zod/v4"));
const types_js_1 = require("../../types.js");
const inMemoryEventStore_js_1 = require("../shared/inMemoryEventStore.js");
const express_js_1 = require("../../server/express.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)
* - /messages: The deprecated POST endpoint for older clients (POST to send messages)
*/
const getServer = () => {
const server = new mcp_js_1.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 }, extra) => {
const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));
let counter = 0;
while (count === 0 || counter < count) {
counter++;
try {
await server.sendLoggingMessage({
level: 'info',
data: `Periodic notification #${counter} at ${new Date().toISOString()}`
}, extra.sessionId);
}
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`
}
]
};
});
return server;
};
// Create Express application
const app = (0, express_js_1.createMcpExpressApp)();
// Store transports by session ID
const transports = {};
//=============================================================================
// 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, res) => {
console.log(`Received ${req.method} request to /mcp`);
try {
// Check for existing session ID
const sessionId = req.headers['mcp-session-id'];
let transport;
if (sessionId && transports[sessionId]) {
// Check if the transport is of the correct type
const existingTransport = transports[sessionId];
if (existingTransport instanceof streamableHttp_js_1.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' && (0, types_js_1.isInitializeRequest)(req.body)) {
const eventStore = new inMemoryEventStore_js_1.InMemoryEventStore();
transport = new streamableHttp_js_1.StreamableHTTPServerTransport({
sessionIdGenerator: () => (0, node_crypto_1.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
const server = getServer();
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, res) => {
console.log('Received GET request to /sse (deprecated SSE transport)');
const transport = new sse_js_1.SSEServerTransport('/messages', res);
transports[transport.sessionId] = transport;
res.on('close', () => {
delete transports[transport.sessionId];
});
const server = getServer();
await server.connect(transport);
});
app.post('/messages', async (req, res) => {
const sessionId = req.query.sessionId;
let transport;
const existingTransport = transports[sessionId];
if (existingTransport instanceof sse_js_1.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, req.body);
}
else {
res.status(400).send('No transport found for sessionId');
}
});
// Start the server
const PORT = 3000;
app.listen(PORT, error => {
if (error) {
console.error('Failed to start server:', error);
process.exit(1);
}
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 /messages (POST)
Usage:
- Establish SSE stream with GET to /sse
- Send requests with POST to /messages?sessionId=<id>
==============================================
`);
});
// 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);
}
}
console.log('Server shutdown complete');
process.exit(0);
});
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