mcp-hub/sample-mcp/index.js

'use strict';

const WebSocket = require('ws');

const HUB_URL = 'wss://mcp.arik.work/ws/register';
const HUB_URL_FALLBACK = 'ws://mcp.arik.work/ws/register';
const SERVICE_ID = 'sample-mcp';
const SECRET = 'dev-secret';

let reconnectDelay = 1000;
let ws = null;
let useTLS = true;

function getHubUrl() {
  return useTLS ? HUB_URL : HUB_URL_FALLBACK;
}

function connect() {
  const url = getHubUrl();
  console.log(`[sample-mcp] Connecting to hub at ${url}`);
  ws = new WebSocket(url);

  ws.on('open', () => {
    reconnectDelay = 1000;
    console.log('[sample-mcp] Connected to hub');
    const registerMsg = { type: 'register', serviceId: SERVICE_ID, secret: SECRET };
    ws.send(JSON.stringify(registerMsg));
    console.log(`[sample-mcp] Sent register: serviceId=${SERVICE_ID}`);
  });

  ws.on('message', (data) => {
    let envelope;
    try {
      envelope = JSON.parse(data);
    } catch (err) {
      console.error('[sample-mcp] Failed to parse message:', err.message);
      return;
    }

    if (envelope.type !== 'mcp-request') {
      console.log(`[sample-mcp] Ignoring message type: ${envelope.type}`);
      return;
    }

    const { requestId, clientSessionId, payload } = envelope;
    console.log(`[sample-mcp] Request received: requestId=${requestId} method=${payload && payload.method}`);

    const method = payload && payload.method;

    // Notifications have no id and need no response
    if (method === 'notifications/initialized') {
      console.log('[sample-mcp] Got notifications/initialized, no response needed');
      return;
    }

    let result;
    switch (method) {
      case 'initialize':
        result = {
          protocolVersion: '2024-11-05',
          capabilities: { tools: {} },
          serverInfo: { name: 'sample-mcp', version: '1.0.0' },
        };
        break;

      case 'tools/list':
        result = {
          tools: [
            {
              name: 'echo',
              description: 'Echoes back the input',
              inputSchema: {
                type: 'object',
                properties: { message: { type: 'string' } },
                required: ['message'],
              },
            },
          ],
        };
        break;

      case 'tools/call': {
        const toolName = payload.params && payload.params.name;
        const args = (payload.params && payload.params.arguments) || {};
        if (toolName === 'echo') {
          result = {
            content: [{ type: 'text', text: `Echo: ${args.message}` }],
          };
        } else {
          const errorResponse = {
            jsonrpc: '2.0',
            id: payload.id,
            error: { code: -32601, message: `Unknown tool: ${toolName}` },
          };
          sendResponse(requestId, clientSessionId, errorResponse);
          return;
        }
        break;
      }

      default:
        console.warn(`[sample-mcp] Unknown method: ${method}`);
        const errorResponse = {
          jsonrpc: '2.0',
          id: payload.id,
          error: { code: -32601, message: `Method not found: ${method}` },
        };
        sendResponse(requestId, clientSessionId, errorResponse);
        return;
    }

    const jsonrpcResponse = { jsonrpc: '2.0', id: payload.id, result };
    sendResponse(requestId, clientSessionId, jsonrpcResponse);
  });

  ws.on('close', (code, reason) => {
    console.log(`[sample-mcp] Disconnected (code=${code} reason=${reason}), reconnecting in ${reconnectDelay}ms`);
    scheduleReconnect();
  });

  ws.on('error', (err) => {
    console.error(`[sample-mcp] WebSocket error: ${err.message}`);
    if (useTLS && err.message && (err.message.includes('ECONNREFUSED') || err.message.includes('certificate') || err.message.includes('connect'))) {
      console.log('[sample-mcp] TLS connection failed, will try ws:// on next attempt');
      useTLS = false;
    }
  });
}

function sendResponse(requestId, clientSessionId, jsonrpcPayload) {
  if (!ws || ws.readyState !== WebSocket.OPEN) {
    console.error('[sample-mcp] Cannot send response: not connected');
    return;
  }
  const envelope = {
    type: 'mcp-response',
    requestId,
    clientSessionId,
    payload: jsonrpcPayload,
  };
  ws.send(JSON.stringify(envelope));
  console.log(`[sample-mcp] Response sent: requestId=${requestId} method=${jsonrpcPayload.result ? 'ok' : 'error'}`);
}

function scheduleReconnect() {
  setTimeout(() => {
    connect();
    reconnectDelay = Math.min(reconnectDelay * 2, 30000);
  }, reconnectDelay);
}

connect();