MCP-SuperAssistant/dist/gateways/stdioToStatelessStreamableHttp.js

import express from 'express';
import cors from 'cors';
import { spawn } from 'child_process';
import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { getVersion } from '../lib/getVersion.js';
import { onSignals } from '../lib/onSignals.js';
import { serializeCorsOrigin } from '../lib/serializeCorsOrigin.js';
const setResponseHeaders = ({ res, headers, }) => Object.entries(headers).forEach(([key, value]) => {
    res.setHeader(key, value);
});
export async function stdioToStatelessStreamableHttp(args) {
    const { stdioCmd, port, host, streamableHttpPath, logger, corsOrigin, healthEndpoints, headers, } = args;
    logger.info(`  - Headers: ${Object(headers).length ? JSON.stringify(headers) : '(none)'}`);
    logger.info(`  - host: ${host}`);
    logger.info(`  - port: ${port}`);
    logger.info(`  - stdio: ${stdioCmd}`);
    logger.info(`  - streamableHttpPath: ${streamableHttpPath}`);
    logger.info(`  - CORS: ${corsOrigin ? `enabled (${serializeCorsOrigin({ corsOrigin })})` : 'disabled'}`);
    logger.info(`  - Health endpoints: ${healthEndpoints.length ? healthEndpoints.join(', ') : '(none)'}`);
    onSignals({ logger });
    const app = express();
    app.use(express.json());
    if (corsOrigin) {
        app.use(cors({ origin: corsOrigin }));
    }
    for (const ep of healthEndpoints) {
        app.get(ep, (_req, res) => {
            setResponseHeaders({
                res,
                headers,
            });
            res.send('ok');
        });
    }
    app.post(streamableHttpPath, async (req, res) => {
        // In stateless mode, create a new instance of transport and server for each request
        // to ensure complete isolation. A single instance would cause request ID collisions
        // when multiple clients connect concurrently.
        try {
            const server = new Server({ name: 'mcp-superassistant-proxy', version: getVersion() }, { capabilities: {} });
            const transport = new StreamableHTTPServerTransport({
                sessionIdGenerator: undefined,
            });
            await server.connect(transport);
            const child = spawn(stdioCmd, { shell: true });
            child.on('exit', (code, signal) => {
                logger.error(`Child exited: code=${code}, signal=${signal}`);
                transport.close();
            });
            let buffer = '';
            child.stdout.on('data', (chunk) => {
                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 → StreamableHttp:', line);
                        try {
                            transport.send(jsonMsg);
                        }
                        catch (e) {
                            logger.error(`Failed to send to StreamableHttp`, e);
                        }
                    }
                    catch {
                        logger.error(`Child non-JSON: ${line}`);
                    }
                });
            });
            child.stderr.on('data', (chunk) => {
                logger.error(`Child stderr: ${chunk.toString('utf8')}`);
            });
            transport.onmessage = (msg) => {
                logger.info(`StreamableHttp → Child: ${JSON.stringify(msg)}`);
                child.stdin.write(JSON.stringify(msg) + '\n');
            };
            transport.onclose = () => {
                logger.info('StreamableHttp connection closed');
                child.kill();
            };
            transport.onerror = (err) => {
                logger.error(`StreamableHttp error:`, err);
                child.kill();
            };
            await transport.handleRequest(req, res, req.body);
        }
        catch (error) {
            logger.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,
                });
            }
        }
    });
    app.get(streamableHttpPath, async (req, res) => {
        logger.info('Received GET MCP request');
        res.writeHead(405).end(JSON.stringify({
            jsonrpc: '2.0',
            error: {
                code: -32000,
                message: 'Method not allowed.',
            },
            id: null,
        }));
    });
    app.delete(streamableHttpPath, async (req, res) => {
        logger.info('Received DELETE MCP request');
        res.writeHead(405).end(JSON.stringify({
            jsonrpc: '2.0',
            error: {
                code: -32000,
                message: 'Method not allowed.',
            },
            id: null,
        }));
    });
    app.listen(port, host, () => {
        logger.info(`Listening on ${host}:${port}`);
        logger.info(`StreamableHttp endpoint: http://${host}:${port}${streamableHttpPath}`);
    });
}
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