streamable-http.ts•4.04 kB
import express from "express";
import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import http from "http";
export function startStreamableHTTPServer(server: Server): http.Server {
const app = express();
app.use(express.json());
app.post("/mcp", async (req: express.Request, res: express.Response) => {
// 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 {
// DNS rebinding protection is disabled by default for backwards compatibility. If you are running this server
// locally, make sure to set DNS_REBINDING_PROTECTION=true
const enableDnsRebindingProtection =
process.env.DNS_REBINDING_PROTECTION === "true";
const allowedHosts = process.env.DNS_REBINDING_ALLOWED_HOST
? [process.env.DNS_REBINDING_ALLOWED_HOST]
: ["127.0.0.1"];
const transport: StreamableHTTPServerTransport =
new StreamableHTTPServerTransport({
sessionIdGenerator: undefined,
enableDnsRebindingProtection,
allowedHosts,
});
res.on("close", () => {
transport.close();
// Note: server.close() should NOT be called here as server is shared
// across all requests. Calling it would close the global MCP Server
// instance and cause the Node.js process to exit. Only the transport
// instance needs to be closed when the HTTP connection ends.
});
await server.connect(transport);
await transport.handleRequest(req, res, req.body);
} catch (error) {
console.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,
});
}
}
});
// SSE notifications not supported in stateless mode
app.get("/mcp", async (req: express.Request, res: express.Response) => {
console.log("Received GET MCP request");
res.writeHead(405).end(
JSON.stringify({
jsonrpc: "2.0",
error: {
code: -32000,
message: "Method not allowed.",
},
id: null,
})
);
});
// Session termination not needed in stateless mode
app.delete("/mcp", async (req: express.Request, res: express.Response) => {
console.log("Received DELETE MCP request");
res.writeHead(405).end(
JSON.stringify({
jsonrpc: "2.0",
error: {
code: -32000,
message: "Method not allowed.",
},
id: null,
})
);
});
app.get("/health", async (req: express.Request, res: express.Response) => {
res.json({ status: "ok" });
});
app.get("/ready", async (req: express.Request, res: express.Response) => {
try {
// We can add more checks if required
// For now, we'll consider the server ready if it can respond to this request
res.json({
status: "ready",
timestamp: new Date().toISOString(),
});
} catch (error) {
console.error("Readiness check failed:", error);
res.status(503).json({
status: "not ready",
reason: "Server initialization incomplete",
timestamp: new Date().toISOString()
});
}
});
let port = 3000;
try {
port = parseInt(process.env.PORT || "3000", 10);
} catch (e) {
console.error(
"Invalid PORT environment variable, using default port 3000."
);
}
const host = process.env.HOST || "localhost";
const httpServer = app.listen(port, host, () => {
console.log(
`mcp-kubernetes-server is listening on port ${port}\nUse the following url to connect to the server:\nhttp://${host}:${port}/mcp`
);
});
return httpServer;
}