Merge pull request #464 from modelcontextprotocol/revert-380-main

Revert "fix: handle the client disconnect so that the server does not crash."

Author: olaservo

server/src/index.ts

@@ -141,7 +141,7 @@ let backingServerTransport: Transport | undefined;
 
 app.get("/mcp", async (req, res) => {
   const sessionId = req.headers["mcp-session-id"] as string;
-  console.log(`GET /mcp for sessionId ${sessionId}`);
+  console.log(`Received GET message for sessionId ${sessionId}`);
   try {
     const transport = webAppTransports.get(
       sessionId,
@@ -160,7 +160,7 @@ app.get("/mcp", async (req, res) => {
 
 app.post("/mcp", async (req, res) => {
   const sessionId = req.headers["mcp-session-id"] as string | undefined;
-  console.log(`POST /mcp for sessionId ${sessionId}`);
+  console.log(`Received POST message for sessionId ${sessionId}`);
   if (!sessionId) {
     try {
       console.log("New streamable-http connection");
@@ -228,7 +228,7 @@ app.post("/mcp", async (req, res) => {
 
 app.get("/stdio", async (req, res) => {
   try {
-    console.log("GET /stdio");
+    console.log("New connection");
 
     try {
       await backingServerTransport?.close();
@@ -254,53 +254,18 @@ app.get("/stdio", async (req, res) => {
     console.log("Created web app transport");
 
     await webAppTransport.start();
-
-    // Handle client disconnection
-    res.on("close", () => {
-      console.log(
-        `Client disconnected from session ${webAppTransport.sessionId}`,
-      );
-      // Clean up the transport map
-      webAppTransports.delete(webAppTransport.sessionId);
-    });
-
-    // Create a stderr handler that checks connection state
-    const stderrHandler = (chunk: Buffer) => {
-      // Only send if the transport exists in our map (meaning it's still active)
-      if (webAppTransports.has(webAppTransport.sessionId)) {
-        webAppTransport
-          .send({
-            jsonrpc: "2.0",
-            method: "notifications/stderr",
-            params: {
-              content: chunk.toString(),
-            },
-          })
-          .catch((error: any) => {
-            console.error(
-              `Error sending stderr data to client: ${error.message}`,
-            );
-            // If we hit an error sending, clean up the transport
-            webAppTransports.delete(webAppTransport.sessionId);
-          });
-      }
-    };
-
-    if ((backingServerTransport as StdioClientTransport).stderr) {
-      (backingServerTransport as StdioClientTransport).stderr!.on(
-        "data",
-        stderrHandler,
-      );
-
-      // Store the handler reference so we can remove it when client disconnects
-      res.on("close", () => {
-        if ((backingServerTransport as StdioClientTransport).stderr) {
-          (
-            backingServerTransport as StdioClientTransport
-          ).stderr!.removeListener("data", stderrHandler);
-        }
-      });
-    }
+    (backingServerTransport as StdioClientTransport).stderr!.on(
+      "data",
+      (chunk) => {
+        webAppTransport.send({
+          jsonrpc: "2.0",
+          method: "notifications/stderr",
+          params: {
+            content: chunk.toString(),
+          },
+        });
+      },
+    );
 
     mcpProxy({
       transportToClient: webAppTransport,
@@ -317,7 +282,7 @@ app.get("/stdio", async (req, res) => {
 app.get("/sse", async (req, res) => {
   try {
     console.log(
-      "GET /sse (NOTE: The sse transport is deprecated and has been replaced by streamable-http)",
+      "New SSE connection. NOTE: The sse transport is deprecated and has been replaced by streamable-http",
     );
 
     try {
@@ -359,7 +324,7 @@ app.get("/sse", async (req, res) => {
 app.post("/message", async (req, res) => {
   try {
     const sessionId = req.query.sessionId;
-    console.log(`POST /message for sessionId ${sessionId}`);
+    console.log(`Received message for sessionId ${sessionId}`);
 
     const transport = webAppTransports.get(
       sessionId as string,
@@ -376,15 +341,13 @@ app.post("/message", async (req, res) => {
 });
 
 app.get("/health", (req, res) => {
-  console.log("GET /health");
   res.json({
     status: "ok",
   });
 });
 
 app.get("/config", (req, res) => {
   try {
-    console.log("GET /config");
     res.json({
       defaultEnvironment,
       defaultCommand: values.env,