DinCoder

import { Request } from 'express'; import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js'; import { randomUUID } from 'node:crypto'; /** * Transport mode configuration */ export enum TransportMode { STATELESS = 'stateless', STATEFUL = 'stateful', } /** * Transport configuration */ export interface TransportConfig { mode: TransportMode; sessionTimeout?: number; // milliseconds } /** * Session manager for stateful mode */ export class SessionManager { private sessions: Map<string, { transport: StreamableHTTPServerTransport; server?: any; // MCP Server instance lastAccess: number; }> = new Map(); private sessionTimeout: number; constructor(sessionTimeout: number = 30 * 60 * 1000) { // 30 minutes default this.sessionTimeout = sessionTimeout; // Clean up expired sessions periodically setInterval(() => this.cleanupSessions(), 60 * 1000); // every minute } /** * Get or create a session */ getSession(sessionId?: string): { transport: StreamableHTTPServerTransport; server?: any; sessionId: string; isNew: boolean; } { const now = Date.now(); if (sessionId && this.sessions.has(sessionId)) { const session = this.sessions.get(sessionId)!; session.lastAccess = now; return { transport: session.transport, server: session.server, sessionId, isNew: false, }; } // Create new session with a generated ID const newSessionId = randomUUID(); const transport = new StreamableHTTPServerTransport({ sessionIdGenerator: () => newSessionId, enableJsonResponse: true, // Enable JSON responses }); // Apply same Content-Type fix and notification handling as stateless transport const originalHandleRequest = transport.handleRequest.bind(transport); transport.handleRequest = async function(req: any, res: any, parsedBody?: unknown) { // Check if this is a notification (no id field) const isNotification = parsedBody && typeof parsedBody === 'object' && 'jsonrpc' in parsedBody && !('id' in parsedBody); const originalWriteHead = res.writeHead; res.writeHead = function(statusCode: number, headers?: any) { // For notifications, change 202 to 204 per MCP spec if (isNotification && statusCode === 202) { return originalWriteHead.call(this, 204, headers); } if (statusCode >= 400 && statusCode < 600) { if (!headers || !headers['Content-Type']) { return originalWriteHead.call(this, statusCode, { ...headers, 'Content-Type': 'application/json' }); } } return originalWriteHead.call(this, statusCode, headers); }; return originalHandleRequest(req, res, parsedBody); }; this.sessions.set(newSessionId, { transport, lastAccess: now, }); return { transport, sessionId: newSessionId, isNew: true, }; } /** * Set server for a session */ setSessionServer(sessionId: string, server: any): void { const session = this.sessions.get(sessionId); if (session) { session.server = server; } } /** * Delete a session */ deleteSession(sessionId: string): boolean { const session = this.sessions.get(sessionId); if (session) { session.transport.close(); this.sessions.delete(sessionId); return true; } return false; } /** * Clean up expired sessions */ private cleanupSessions(): void { const now = Date.now(); const expired: string[] = []; for (const [id, session] of this.sessions) { if (now - session.lastAccess > this.sessionTimeout) { expired.push(id); } } for (const id of expired) { console.error(`Cleaning up expired session: ${id}`); this.deleteSession(id); } } /** * Get count of active sessions */ getSessionCount(): number { return this.sessions.size; } /** * Close all sessions */ closeAll(): void { for (const [id] of this.sessions) { this.deleteSession(id); } } } /** * Creates a stateless transport (new instance per request) * Wraps the transport to ensure proper Content-Type headers */ export function createStatelessTransport(): StreamableHTTPServerTransport { const transport = new StreamableHTTPServerTransport({ sessionIdGenerator: undefined, // No session management enableJsonResponse: true, // Enable JSON responses for simple request/response }); // Monkey-patch handleRequest to ensure Content-Type is set and handle notifications properly const originalHandleRequest = transport.handleRequest.bind(transport); transport.handleRequest = async function(req: any, res: any, parsedBody?: unknown) { // Check if this is a notification (no id field) const isNotification = parsedBody && typeof parsedBody === 'object' && 'jsonrpc' in parsedBody && !('id' in parsedBody); // Intercept writeHead to ensure Content-Type is set for JSON responses const originalWriteHead = res.writeHead; res.writeHead = function(statusCode: number, headers?: any) { // For notifications, change 202 to 204 per MCP spec if (isNotification && statusCode === 202) { return originalWriteHead.call(this, 204, headers); } // If sending an error status and no Content-Type set, add it if (statusCode >= 400 && statusCode < 600) { if (!headers || !headers['Content-Type']) { return originalWriteHead.call(this, statusCode, { ...headers, 'Content-Type': 'application/json' }); } } return originalWriteHead.call(this, statusCode, headers); }; return originalHandleRequest(req, res, parsedBody); }; return transport; } /** * Validates session ID format * Must contain only visible ASCII characters (0x21 to 0x7E) */ export function isValidSessionId(sessionId: string): boolean { if (!sessionId || sessionId.length === 0) { return false; } for (let i = 0; i < sessionId.length; i++) { const code = sessionId.charCodeAt(i); if (code < 0x21 || code > 0x7E) { return false; } } return true; } /** * Extracts session ID from request headers */ export function getSessionIdFromRequest(req: Request): string | undefined { const sessionId = req.headers['mcp-session-id'] as string | undefined; if (sessionId && !isValidSessionId(sessionId)) { throw new Error('Invalid session ID format'); } return sessionId; } /** * Checks if request is an initialization request */ export function isInitRequest(body: unknown): boolean { // Simple check - just look for method === 'initialize' // The SDK's isInitializeRequest is too strict and requires clientInfo if (body && typeof body === 'object' && 'method' in body) { return (body as any).method === 'initialize'; } return false; } /** * Gets protocol version from request */ export function getProtocolVersion(req: Request): string { return (req.headers['mcp-protocol-version'] as string) || '2025-03-26'; }