feat: add HTTP/SSE transport option with --transportType and --port support

Add support and documentation for running the MCP server with HTTP or SSE transport using --transportType and --port arguments
Provide example commands and clarify default port usage for custom network endpoints

Author: Rujaxx

package.json

@@ -37,6 +37,7 @@
     "@jest/globals": "^29.7.0",
     "@modelcontextprotocol/inspector": "^0.10.2",
     "@redocly/cli": "^1.34.2",
+    "@types/express": "^5.0.1",
     "@types/jest": "^29.5.14",
     "@types/node": "^22.14.0",
     "@types/simple-oauth2": "^5.0.7",
@@ -65,6 +66,7 @@
     "@mongodb-js/devtools-connect": "^3.7.2",
     "@mongosh/service-provider-node-driver": "^3.6.0",
     "bson": "^6.10.3",
+    "express": "^5.1.0",
     "lru-cache": "^11.1.0",
     "mongodb": "^6.15.0",
     "mongodb-connection-string-url": "^3.0.2",

src/config.ts

@@ -23,6 +23,8 @@ export interface UserConfig {
     connectOptions: ConnectOptions;
     disabledTools: Array<string>;
     readOnly?: boolean;
+    transportType?: "stdio" | "sse" | "http";
+    port: string;
 }
 
 const defaults: UserConfig = {
@@ -37,6 +39,8 @@ const defaults: UserConfig = {
     disabledTools: [],
     telemetry: "enabled",
     readOnly: false,
+    transportType: "stdio",
+    port: "5700",
 };
 
 export const config = {

src/index.ts

@@ -2,6 +2,10 @@
 
 import logger, { LogId } from "./logger.js";
 import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+import express from "express";
+import { randomUUID } from "node:crypto";
+import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
+import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js";
 import { config } from "./config.js";
 import { Session } from "./session.js";
 import { Server } from "./server.js";
@@ -29,9 +33,81 @@ try {
         userConfig: config,
     });
 
-    const transport = createEJsonTransport();
+    if (config.transportType === "http" || config.transportType === "sse") {
+        const app = express();
+        app.use(express.json());
 
-    await server.connect(transport);
+        // Map to store transports by session ID
+        const transports: { [sessionId: string]: StreamableHTTPServerTransport } = {};
+
+        // Handle POST requests for client-to-server communication
+        app.post("/mcp", async (req, res) => {
+            // Check for existing session ID
+            const sessionId = req.headers["mcp-session-id"] as string | undefined;
+            let transport: StreamableHTTPServerTransport;
+
+            if (sessionId && transports[sessionId]) {
+                // Reuse existing transport
+                transport = transports[sessionId];
+            } else if (!sessionId && isInitializeRequest(req.body)) {
+                // New initialization request
+                transport = new StreamableHTTPServerTransport({
+                    sessionIdGenerator: () => randomUUID(),
+                    onsessioninitialized: (sessionId: string) => {
+                        // Store the transport by session ID
+                        transports[sessionId] = transport;
+                    },
+                });
+
+                // Clean up transport when closed
+                transport.onclose = () => {
+                    if (transport.sessionId) {
+                        delete transports[transport.sessionId];
+                    }
+                };
+
+                // Connect to the MCP server
+                await server.connect(transport);
+            } else {
+                // Invalid request
+                res.status(400).json({
+                    jsonrpc: "2.0",
+                    error: {
+                        code: -32000,
+                        message: "Bad Request: No valid session ID provided",
+                    },
+                    id: null,
+                });
+                return;
+            }
+
+            // Handle the request
+            await transport.handleRequest(req, res, req.body);
+        });
+
+        // Reusable handler for GET and DELETE requests
+        const handleSessionRequest = async (req: express.Request, res: express.Response) => {
+            const sessionId = req.headers["mcp-session-id"] as string | undefined;
+            if (!sessionId || !transports[sessionId]) {
+                res.status(400).send("Invalid or missing session ID");
+                return;
+            }
+
+            const transport = transports[sessionId];
+            await transport.handleRequest(req, res);
+        };
+
+        // Handle GET requests for server-to-client notifications via SSE
+        app.get("/mcp", handleSessionRequest);
+
+        // Handle DELETE requests for session termination
+        app.delete("/mcp", handleSessionRequest);
+        const PORT = config.port;
+        app.listen(PORT);
+    } else {
+        const transport = createEJsonTransport();
+        await server.connect(transport);
+    }
 } catch (error: unknown) {
     logger.emergency(LogId.serverStartFailure, "server", `Fatal error running server: ${error as string}`);
     process.exit(1);