Email MCP Server

import express from 'express' import cors, { type CorsOptions } from 'cors' import { createServer } from 'http' import { spawn, ChildProcessWithoutNullStreams } from 'child_process' import { Server } from '@modelcontextprotocol/sdk/server/index.js' import { JSONRPCMessage } from '@modelcontextprotocol/sdk/types.js' import { Logger } from '../types.js' import { getVersion } from '../lib/getVersion.js' import { WebSocketServerTransport } from '../server/websocket.js' import { onSignals } from '../lib/onSignals.js' import { serializeCorsOrigin } from '../lib/serializeCorsOrigin.js' export interface StdioToWsArgs { stdioCmd: string port: number messagePath: string logger: Logger corsOrigin: CorsOptions['origin'] healthEndpoints: string[] } export async function stdioToWs(args: StdioToWsArgs) { const { stdioCmd, port, messagePath, logger, healthEndpoints, corsOrigin } = args logger.info(` - port: ${port}`) logger.info(` - stdio: ${stdioCmd}`) logger.info(` - messagePath: ${messagePath}`) logger.info( ` - CORS: ${corsOrigin ? `enabled (${serializeCorsOrigin({ corsOrigin })})` : 'disabled'}`, ) logger.info( ` - Health endpoints: ${healthEndpoints.length ? healthEndpoints.join(', ') : '(none)'}`, ) let wsTransport: WebSocketServerTransport | null = null let child: ChildProcessWithoutNullStreams | null = null let isReady = false const cleanup = () => { if (wsTransport) { wsTransport.close().catch((err) => { logger.error(`Error stopping WebSocket server: ${err.message}`) }) } if (child) { child.kill() } } onSignals({ logger, cleanup, }) try { child = spawn(stdioCmd, { shell: true }) child.on('exit', (code, signal) => { logger.error(`Child exited: code=${code}, signal=${signal}`) cleanup() process.exit(code ?? 1) }) const server = new Server( { name: 'supergateway', version: getVersion() }, { capabilities: {} }, ) // Handle child process output let buffer = '' child.stdout.on('data', (chunk: Buffer) => { buffer += chunk.toString('utf8') const lines = buffer.split(/\r?\n/) buffer = lines.pop() ?? '' lines.forEach((line) => { if (!line.trim()) return try { const jsonMsg = JSON.parse(line) logger.info(`Child → WebSocket: ${JSON.stringify(jsonMsg)}`) // Broadcast to all connected clients wsTransport?.send(jsonMsg, jsonMsg.id).catch((err) => { logger.error('Failed to broadcast message:', err) }) } catch { logger.error(`Child non-JSON: ${line}`) } }) }) child.stderr.on('data', (chunk: Buffer) => { logger.info(`Child stderr: ${chunk.toString('utf8')}`) }) const app = express() if (corsOrigin) { app.use(cors({ origin: corsOrigin })) } for (const ep of healthEndpoints) { app.get(ep, (_req, res) => { if (child?.killed) { res.status(500).send('Child process has been killed') } if (!isReady) { res.status(500).send('Server is not ready') } res.send('ok') }) } const httpServer = createServer(app) wsTransport = new WebSocketServerTransport({ path: messagePath, server: httpServer, }) await server.connect(wsTransport) wsTransport.onmessage = (msg: JSONRPCMessage) => { const line = JSON.stringify(msg) logger.info(`WebSocket → Child: ${line}`) child!.stdin.write(line + '\n') } wsTransport.onconnection = (clientId: string) => { logger.info(`New WebSocket connection: ${clientId}`) } wsTransport.ondisconnection = (clientId: string) => { logger.info(`WebSocket connection closed: ${clientId}`) } wsTransport.onerror = (err: Error) => { logger.error(`WebSocket error: ${err.message}`) } isReady = true httpServer.listen(port, () => { logger.info(`Listening on port ${port}`) logger.info(`WebSocket endpoint: ws://localhost:${port}${messagePath}`) }) } catch (err: any) { logger.error(`Failed to start: ${err.message}`) cleanup() process.exit(1) } }