Streamable HTTP & SSE

Remote Connections (2025 Spec)

If you want to host an MCP Server in the cloud (e.g., on Vercel or AWS) so multiple clients can connect, you use the Streamable HTTP transport, historically involving Server-Sent Events (SSE).

How it Works

1. The Client connects to the Server's HTTP endpoint.
2. The Server establishes an SSE connection to push events to the Client asynchronously.
3. The Client sends requests to the Server via standard HTTP POST requests.

This allows a single cloud-hosted MCP Server to serve thousands of Clients independently.

import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
app.get("/sse", async (req, res) => {
  const transport = new SSEServerTransport("/message", res);
  await server.connect(transport);
});