initialize project

src/index.ts

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+import express, { Request, Response } from 'express';
+import dotenv from 'dotenv';
+import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
+import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
+import { registerAllTools } from './server.js';
+
+dotenv.config();
+
+const server = new McpServer({
+  name: 'mcphub',
+  version: '0.0.1',
+});
+
+// Register all MCP tools from the modular structure
+registerAllTools(server);
+
+const app = express();
+const PORT = process.env.PORT || 3000;
+
+// to support multiple simultaneous connections we have a lookup object from sessionId to transport
+const transports: { [sessionId: string]: SSEServerTransport } = {};
+
+app.get('/sse', async (_: Request, res: Response) => {
+  const transport = new SSEServerTransport('/messages', res);
+  transports[transport.sessionId] = transport;
+  res.on('close', () => {
+    delete transports[transport.sessionId];
+  });
+  await server.connect(transport);
+});
+
+app.post('/messages', async (req: Request, res: Response) => {
+  const sessionId = req.query.sessionId as string;
+  const transport = transports[sessionId];
+  if (transport) {
+    await transport.handlePostMessage(req, res);
+  } else {
+    console.error(`No transport found for sessionId: ${sessionId}`);
+    res.status(400).send('No transport found for sessionId');
+  }
+});
+
+app.listen(PORT, () => {
+  console.log(`Server is running on port ${PORT}`);
+});
+
+export default app;

src/server.ts

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+import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
+import { Client } from '@modelcontextprotocol/sdk/client/index.js';
+import { SSEClientTransport } from '@modelcontextprotocol/sdk/client/sse.js';
+import { ZodType, ZodRawShape } from 'zod';
+
+const transport = new SSEClientTransport(new URL('http://localhost:3001/sse'));
+
+const client = new Client(
+  {
+    name: 'example-client',
+    version: '1.0.0',
+  },
+  {
+    capabilities: {
+      prompts: {},
+      resources: {},
+      tools: {},
+    },
+  },
+);
+
+export const registerAllTools = async (server: McpServer) => {
+  await client.connect(transport);
+  const tools = await client.listTools();
+  for (const tool of tools.tools) {
+    await server.tool(
+      tool.name,
+      tool.description || '',
+      cast(tool.inputSchema.properties),
+      async (params) => {
+        const result = await client.callTool({
+          name: tool.name,
+          arguments: params,
+        });
+        return { content: [{ type: 'text', text: JSON.stringify(result) }] };
+      },
+    );
+  }
+};
+
+function cast(inputSchema: unknown): ZodRawShape {
+  if (typeof inputSchema !== 'object' || inputSchema === null) {
+    throw new Error('Invalid input schema');
+  }
+
+  const castedSchema = inputSchema as ZodRawShape;
+
+  for (const key in castedSchema) {
+    if (castedSchema[key] instanceof ZodType) {
+      castedSchema[key] = castedSchema[key].optional() as ZodType;
+    }
+  }
+
+  return castedSchema;
+}