index.ts•4.68 kB
import express from "express";
import cors from "cors";
import { randomUUID } from "node:crypto";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js";
import { createMcpServer } from "./server.js";
const app = express();
const PORT = process.env.PORT || 8080;
// CORS configuration for browser-based clients
app.use(cors({
origin: '*', // Configure appropriately for production
exposedHeaders: ['Mcp-Session-Id'],
allowedHeaders: ['Content-Type', 'mcp-session-id'],
}));
app.use(express.json());
// Map to store transports by session ID
const transports: { [sessionId: string]: StreamableHTTPServerTransport } = {};
// Health check endpoint
app.get('/health', (req, res) => {
res.status(200).json({
status: 'ok',
timestamp: new Date().toISOString(),
service: 'kleros-mcp-server'
});
});
// Main MCP endpoint
app.post('/mcp', async (req, res) => {
try {
// Check for existing session ID
const sessionId = req.headers['mcp-session-id'] as string | undefined;
let transport: StreamableHTTPServerTransport;
if (sessionId && transports[sessionId]) {
// Reuse existing transport
transport = transports[sessionId];
} else if (!sessionId && isInitializeRequest(req.body)) {
// New initialization request
transport = new StreamableHTTPServerTransport({
sessionIdGenerator: () => randomUUID(),
onsessioninitialized: (sessionId) => {
// Store the transport by session ID
transports[sessionId] = transport;
console.log(`New MCP session initialized: ${sessionId}`);
},
// Enable DNS rebinding protection for security
enableDnsRebindingProtection: true,
allowedHosts: process.env.ALLOWED_HOSTS ? process.env.ALLOWED_HOSTS.split(',') : ['localhost', '127.0.0.1'],
});
// Clean up transport when closed
transport.onclose = () => {
if (transport.sessionId) {
delete transports[transport.sessionId];
console.log(`MCP session closed: ${transport.sessionId}`);
}
};
// Create and connect MCP server
const mcpServer = createMcpServer();
await mcpServer.connect(transport);
} else {
// Invalid request
res.status(400).json({
jsonrpc: '2.0',
error: {
code: -32000,
message: 'Bad Request: No valid session ID provided or invalid initialization request',
},
id: null,
});
return;
}
// Handle the request
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,
});
}
}
});
// Reusable handler for GET and DELETE requests
const handleSessionRequest = async (req: express.Request, res: express.Response) => {
const sessionId = req.headers['mcp-session-id'] as string | undefined;
if (!sessionId || !transports[sessionId]) {
res.status(400).send('Invalid or missing session ID');
return;
}
const transport = transports[sessionId];
await transport.handleRequest(req, res);
};
// Handle GET requests for server-to-client notifications via SSE
app.get('/mcp', handleSessionRequest);
// Handle DELETE requests for session termination
app.delete('/mcp', handleSessionRequest);
// Error handling middleware
app.use((error: Error, req: express.Request, res: express.Response, next: express.NextFunction) => {
console.error('Unhandled error:', error);
if (!res.headersSent) {
res.status(500).json({
error: 'Internal server error',
message: process.env.NODE_ENV === 'development' ? error.message : 'Something went wrong'
});
}
});
// 404 handler
app.use((req, res) => {
res.status(404).json({
error: 'Not Found',
message: `Route ${req.method} ${req.path} not found`
});
});
// Start the server
app.listen(PORT, () => {
console.log(`Kleros MCP Server listening on port ${PORT}`);
console.log(`Health check: http://localhost:${PORT}/health`);
console.log(`MCP endpoint: http://localhost:${PORT}/mcp`);
console.log(`Environment: ${process.env.NODE_ENV || 'development'}`);
});
// Graceful shutdown
process.on('SIGTERM', () => {
console.log('SIGTERM received, shutting down gracefully');
process.exit(0);
});
process.on('SIGINT', () => {
console.log('SIGINT received, shutting down gracefully');
process.exit(0);
});