MCP Fetch

import { WebSocketServer, WebSocket } from 'ws' import { Server } from 'http' interface ClientInfo { id: string connected: Date messageCount: number } export function createWebSocketMockServer(httpServer: Server) { const wss = new WebSocketServer({ server: httpServer, path: '/ws' }) const clients = new Map<WebSocket, ClientInfo>() wss.on('connection', (ws: WebSocket, request) => { const clientId = `client-${Date.now()}-${Math.random().toString(36).substr(2, 9)}` // Store client info clients.set(ws, { id: clientId, connected: new Date(), messageCount: 0 }) // Declare ping interval variable let pingInterval: NodeJS.Timeout // Send welcome message ws.send(JSON.stringify({ type: 'connection', message: 'Connected to mock WebSocket server', clientId, timestamp: new Date().toISOString() })) // Echo messages back to client (mimicking echo.websocket.org) ws.on('message', (data: Buffer) => { const clientInfo = clients.get(ws)! clientInfo.messageCount++ const message = data.toString() // Echo the message back ws.send(message) // Also send a metadata message if the message is JSON try { const parsed = JSON.parse(message) ws.send(JSON.stringify({ type: 'echo-metadata', originalMessage: parsed, echoedAt: new Date().toISOString(), messageNumber: clientInfo.messageCount })) } catch { // Not JSON, just echo as-is } }) ws.on('close', (code, reason) => { const clientInfo = clients.get(ws) clients.delete(ws) // Clear ping interval when connection closes if (pingInterval) { clearInterval(pingInterval) } }) ws.on('error', (error) => { const clientInfo = clients.get(ws) // Handle error silently }) // Ping client every 5 seconds to keep connection alive (shorter for tests) pingInterval = setInterval(() => { if (ws.readyState === WebSocket.OPEN) { ws.ping() } else { clearInterval(pingInterval) } }, 5000) // Allow the process to exit even if this timer is active pingInterval.unref() ws.on('pong', () => { const clientInfo = clients.get(ws) // Pong received }) }) // Add a status endpoint for debugging const getStatus = () => ({ connectedClients: clients.size, clients: Array.from(clients.entries()).map(([ws, info]) => ({ id: info.id, connected: info.connected, messageCount: info.messageCount, readyState: ws.readyState, readyStateString: ['CONNECTING', 'OPEN', 'CLOSING', 'CLOSED'][ws.readyState] })) }) return { wss, getStatus } }