feat: add generic mcp-bridge for proxying upstream MCP SSE servers
- Add mcp-bridge/index.js: WebSocket backend for hub, relays requests to upstream MCP SSE servers via SSE+POST transport - Add mcp-bridge/package.json with 'ws' dependency - Add 'mcp-bridge-memory' entry to ecosystem.config.js (not started) - Add 'bridge' script to root package.json - Add mcp-bridge/node_modules to .gitignore Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Agent
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1
.gitignore
vendored
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.gitignore
vendored
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@ -1,3 +1,4 @@
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agent_gateway.db
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node_modules/
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.env
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mcp-bridge/node_modules
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@ -19,6 +19,17 @@ module.exports = {
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restart_delay: 2000,
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log_date_format: 'YYYY-MM-DD HH:mm:ss Z',
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merge_logs: true
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},
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{
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name: 'mcp-bridge-memory',
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script: 'mcp-bridge/index.js',
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cwd: '/workspace',
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env: {
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BRIDGE_SERVICE_ID: 'memory-mcp',
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BRIDGE_SECRET: 'dev-secret',
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BRIDGE_HUB_URL: 'ws://localhost:3000/ws/register',
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BRIDGE_UPSTREAM_URL: 'https://memory-mcp.dbchat.ai/mcp/sse'
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}
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}
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]
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};
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287
mcp-bridge/index.js
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287
mcp-bridge/index.js
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'use strict';
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const WebSocket = require('ws');
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const http = require('http');
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const https = require('https');
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const { URL } = require('url');
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const SERVICE_ID = process.env.BRIDGE_SERVICE_ID || 'memory-mcp';
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const SECRET = process.env.BRIDGE_SECRET || 'dev-secret';
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const HUB_URL = process.env.BRIDGE_HUB_URL || 'ws://localhost:3000/ws/register';
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const UPSTREAM_URL = process.env.BRIDGE_UPSTREAM_URL || 'https://memory-mcp.dbchat.ai/mcp/sse';
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// Map of clientSessionId -> { req (IncomingMessage), postUrl, pendingRequests: Map<jsonrpcId -> requestId> }
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const sessions = new Map();
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let ws = null;
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let reconnectDelay = 1000;
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function log(...args) {
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console.log(new Date().toISOString(), '[mcp-bridge]', ...args);
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}
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function sendToHub(obj) {
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if (ws && ws.readyState === WebSocket.OPEN) {
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ws.send(JSON.stringify(obj));
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}
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}
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function closeSession(clientSessionId) {
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const session = sessions.get(clientSessionId);
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if (session) {
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log(`Closing upstream session for clientSessionId=${clientSessionId}`);
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try { session.req.destroy(); } catch (_) {}
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sessions.delete(clientSessionId);
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}
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}
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function openUpstreamSession(clientSessionId, onReady) {
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const upstreamUrl = new URL(UPSTREAM_URL);
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const isHttps = upstreamUrl.protocol === 'https:';
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const lib = isHttps ? https : http;
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const options = {
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hostname: upstreamUrl.hostname,
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port: upstreamUrl.port || (isHttps ? 443 : 80),
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path: upstreamUrl.pathname + upstreamUrl.search,
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method: 'GET',
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headers: {
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'Accept': 'text/event-stream',
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'Cache-Control': 'no-cache'
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}
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};
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log(`Opening upstream SSE connection for clientSessionId=${clientSessionId} -> ${UPSTREAM_URL}`);
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const req = lib.request(options, (res) => {
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if (res.statusCode !== 200) {
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log(`Upstream SSE returned HTTP ${res.statusCode} for clientSessionId=${clientSessionId}`);
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req.destroy();
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onReady(new Error(`Upstream SSE HTTP ${res.statusCode}`));
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return;
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}
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const session = {
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req,
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postUrl: null,
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pendingRequests: new Map()
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};
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sessions.set(clientSessionId, session);
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let buffer = '';
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let currentEvent = null;
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res.on('data', (chunk) => {
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buffer += chunk.toString();
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const lines = buffer.split('\n');
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buffer = lines.pop(); // keep incomplete last line
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for (const line of lines) {
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if (line.startsWith('event:')) {
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currentEvent = line.slice(6).trim();
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} else if (line.startsWith('data:')) {
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const data = line.slice(5).trim();
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if (currentEvent === 'endpoint') {
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// Resolve relative path against upstream origin
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let postUrl;
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if (data.startsWith('http://') || data.startsWith('https://')) {
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postUrl = data;
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} else {
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postUrl = `${upstreamUrl.protocol}//${upstreamUrl.host}${data}`;
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}
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session.postUrl = postUrl;
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log(`Got upstream POST URL for clientSessionId=${clientSessionId}: ${postUrl}`);
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onReady(null);
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} else if (currentEvent === 'message' || currentEvent === null) {
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// JSON-RPC response from upstream
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let msg;
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try {
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msg = JSON.parse(data);
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} catch (e) {
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log(`Failed to parse upstream SSE message: ${data}`);
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return;
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}
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if (msg.id !== undefined && msg.id !== null) {
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const key = `${clientSessionId}:${msg.id}`;
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const requestId = session.pendingRequests.get(key);
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if (requestId) {
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session.pendingRequests.delete(key);
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log(`Relaying response to hub: requestId=${requestId} jsonrpcId=${msg.id}`);
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sendToHub({
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type: 'mcp-response',
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requestId,
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clientSessionId,
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payload: msg
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});
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} else {
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log(`No pending request for key=${key}, dropping response`);
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}
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} else {
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// Notification — no requestId needed, just log
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log(`Received upstream notification for clientSessionId=${clientSessionId}:`, JSON.stringify(msg));
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}
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}
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currentEvent = null;
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} else if (line === '') {
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currentEvent = null;
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}
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}
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});
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res.on('end', () => {
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log(`Upstream SSE stream ended for clientSessionId=${clientSessionId}`);
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closeSession(clientSessionId);
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});
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res.on('error', (err) => {
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log(`Upstream SSE stream error for clientSessionId=${clientSessionId}:`, err.message);
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closeSession(clientSessionId);
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});
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});
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req.on('error', (err) => {
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log(`Upstream SSE request error for clientSessionId=${clientSessionId}:`, err.message);
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sessions.delete(clientSessionId);
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onReady(err);
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});
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req.end();
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}
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function postToUpstream(postUrl, payload, callback) {
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const body = JSON.stringify(payload);
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const url = new URL(postUrl);
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const isHttps = url.protocol === 'https:';
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const lib = isHttps ? https : http;
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const options = {
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hostname: url.hostname,
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port: url.port || (isHttps ? 443 : 80),
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path: url.pathname + url.search,
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method: 'POST',
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headers: {
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'Content-Type': 'application/json',
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'Content-Length': Buffer.byteLength(body)
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}
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};
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const req = lib.request(options, (res) => {
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let data = '';
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res.on('data', (chunk) => { data += chunk; });
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res.on('end', () => {
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if (res.statusCode < 200 || res.statusCode >= 300) {
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callback(new Error(`POST to upstream returned HTTP ${res.statusCode}: ${data}`));
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} else {
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callback(null);
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}
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});
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});
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req.on('error', callback);
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req.write(body);
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req.end();
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}
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function handleMcpRequest(msg) {
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const { requestId, clientSessionId, payload } = msg;
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const forwardRequest = () => {
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const session = sessions.get(clientSessionId);
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if (!session || !session.postUrl) {
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log(`No postUrl available for clientSessionId=${clientSessionId}, dropping request`);
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return;
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}
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// Track pending request if payload has an id
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if (payload.id !== undefined && payload.id !== null) {
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const key = `${clientSessionId}:${payload.id}`;
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session.pendingRequests.set(key, requestId);
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log(`Forwarding request: requestId=${requestId} clientSessionId=${clientSessionId} method=${payload.method} jsonrpcId=${payload.id}`);
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} else {
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log(`Forwarding notification: clientSessionId=${clientSessionId} method=${payload.method}`);
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}
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postToUpstream(session.postUrl, payload, (err) => {
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if (err) {
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log(`Error posting to upstream for clientSessionId=${clientSessionId}:`, err.message);
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if (payload.id !== undefined && payload.id !== null) {
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const key = `${clientSessionId}:${payload.id}`;
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session.pendingRequests.delete(key);
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}
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}
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});
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};
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if (!sessions.has(clientSessionId)) {
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openUpstreamSession(clientSessionId, (err) => {
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if (err) {
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log(`Failed to open upstream session for clientSessionId=${clientSessionId}:`, err.message);
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return;
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}
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forwardRequest();
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});
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} else {
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const session = sessions.get(clientSessionId);
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if (!session.postUrl) {
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// Still waiting for endpoint event — retry shortly
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log(`Session exists but postUrl not yet available for clientSessionId=${clientSessionId}, retrying...`);
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setTimeout(forwardRequest, 200);
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} else {
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forwardRequest();
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}
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}
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}
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function connect() {
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log(`Connecting to hub: ${HUB_URL}`);
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ws = new WebSocket(HUB_URL);
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ws.on('open', () => {
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reconnectDelay = 1000;
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log(`Connected to hub, registering as serviceId=${SERVICE_ID}`);
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ws.send(JSON.stringify({ type: 'register', serviceId: SERVICE_ID, secret: SECRET }));
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});
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ws.on('message', (data) => {
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let msg;
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try {
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msg = JSON.parse(data.toString());
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} catch (e) {
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log('Failed to parse hub message:', data.toString());
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return;
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}
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if (msg.type === 'registered') {
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log(`Registered with hub as serviceId=${SERVICE_ID}`);
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} else if (msg.type === 'mcp-request') {
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handleMcpRequest(msg);
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} else {
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log('Unknown message from hub:', msg.type);
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}
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});
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ws.on('close', (code, reason) => {
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log(`Hub WebSocket closed (code=${code}), cleaning up all sessions`);
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for (const clientSessionId of sessions.keys()) {
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closeSession(clientSessionId);
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}
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scheduleReconnect();
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});
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ws.on('error', (err) => {
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log('Hub WebSocket error:', err.message);
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});
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}
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function scheduleReconnect() {
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log(`Reconnecting in ${reconnectDelay}ms...`);
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setTimeout(() => {
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connect();
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}, reconnectDelay);
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reconnectDelay = Math.min(reconnectDelay * 2, 30000);
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}
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connect();
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37
mcp-bridge/package-lock.json
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37
mcp-bridge/package-lock.json
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{
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"name": "mcp-bridge",
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"version": "1.0.0",
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"lockfileVersion": 3,
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"requires": true,
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"packages": {
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"": {
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"name": "mcp-bridge",
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"version": "1.0.0",
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"license": "ISC",
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"dependencies": {
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"ws": "^8.19.0"
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}
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},
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"node_modules/ws": {
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"version": "8.19.0",
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"resolved": "https://registry.npmjs.org/ws/-/ws-8.19.0.tgz",
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"integrity": "sha512-blAT2mjOEIi0ZzruJfIhb3nps74PRWTCz1IjglWEEpQl5XS/UNama6u2/rjFkDDouqr4L67ry+1aGIALViWjDg==",
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"license": "MIT",
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"engines": {
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"node": ">=10.0.0"
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},
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"peerDependencies": {
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"bufferutil": "^4.0.1",
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"utf-8-validate": ">=5.0.2"
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},
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"peerDependenciesMeta": {
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"bufferutil": {
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"optional": true
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},
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"utf-8-validate": {
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"optional": true
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}
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}
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}
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}
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}
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13
mcp-bridge/package.json
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13
mcp-bridge/package.json
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{
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"name": "mcp-bridge",
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"version": "1.0.0",
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"description": "Generic MCP SSE bridge for the MCP hub",
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"main": "index.js",
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"scripts": {
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"start": "node index.js"
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},
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"dependencies": {
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"ws": "^8.19.0"
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},
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"license": "ISC"
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}
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"scripts": {
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"test": "node test/e2e.js",
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"start": "node src/index.js",
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"bridge": "node mcp-bridge/index.js",
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"sample-mcp": "node sample-mcp/index.js",
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"pm2:start": "pm2 start ecosystem.config.js",
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"pm2:stop": "pm2 stop all",
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