Merge pull request #749 from modelcontextprotocol/ochafik/check-addrinuse

Add missing app.listen error handling to server examples

Author: ihrpr

src/cli.ts

@@ -102,7 +102,11 @@ async function runServer(port: number | null) {
       await transport.handlePostMessage(req, res);
     });
 
-    app.listen(port, () => {
+    app.listen(port, (error) => {
+      if (error) {
+        console.error('Failed to start server:', error);
+        process.exit(1);
+      }
       console.log(`Server running on http://localhost:${port}/sse`);
     });
   } else {

src/examples/server/demoInMemoryOAuthProvider.ts

@@ -200,7 +200,11 @@ export const setupAuthServer = ({authServerUrl, mcpServerUrl, strictResource}: {
 
   const auth_port = authServerUrl.port;
   // Start the auth server
-  authApp.listen(auth_port, () => {
+  authApp.listen(auth_port, (error) => {
+    if (error) {
+      console.error('Failed to start server:', error);
+      process.exit(1);
+    }
     console.log(`OAuth Authorization Server listening on port ${auth_port}`);
   });
 

src/examples/server/jsonResponseStreamableHttp.ts

@@ -158,7 +158,11 @@ app.get('/mcp', async (req: Request, res: Response) => {
 
 // Start the server
 const PORT = 3000;
-app.listen(PORT, () => {
+app.listen(PORT, (error) => {
+  if (error) {
+    console.error('Failed to start server:', error);
+    process.exit(1);
+  }
   console.log(`MCP Streamable HTTP Server listening on port ${PORT}`);
 });
 

src/examples/server/simpleSseServer.ts

@@ -145,7 +145,11 @@ app.post('/messages', async (req: Request, res: Response) => {
 
 // Start the server
 const PORT = 3000;
-app.listen(PORT, () => {
+app.listen(PORT, (error) => {
+  if (error) {
+    console.error('Failed to start server:', error);
+    process.exit(1);
+  }
   console.log(`Simple SSE Server (deprecated protocol version 2024-11-05) listening on port ${PORT}`);
 });
 

src/examples/server/simpleStatelessStreamableHttp.ts

@@ -158,7 +158,11 @@ app.delete('/mcp', async (req: Request, res: Response) => {
 
 // Start the server
 const PORT = 3000;
-app.listen(PORT, () => {
+app.listen(PORT, (error) => {
+  if (error) {
+    console.error('Failed to start server:', error);
+    process.exit(1);
+  }
   console.log(`MCP Stateless Streamable HTTP Server listening on port ${PORT}`);
 });
 

src/examples/server/simpleStreamableHttp.ts

@@ -648,7 +648,11 @@ if (useOAuth && authMiddleware) {
   app.delete('/mcp', mcpDeleteHandler);
 }
 
-app.listen(MCP_PORT, () => {
+app.listen(MCP_PORT, (error) => {
+  if (error) {
+    console.error('Failed to start server:', error);
+    process.exit(1);
+  }
   console.log(`MCP Streamable HTTP Server listening on port ${MCP_PORT}`);
 });
 

src/examples/server/sseAndStreamableHttpCompatibleServer.ts

@@ -210,7 +210,11 @@ app.post("/messages", async (req: Request, res: Response) => {
 
 // Start the server
 const PORT = 3000;
-app.listen(PORT, () => {
+app.listen(PORT, (error) => {
+  if (error) {
+    console.error('Failed to start server:', error);
+    process.exit(1);
+  }
   console.log(`Backwards compatible MCP server listening on port ${PORT}`);
   console.log(`
 ==============================================

src/examples/server/standaloneSseWithGetStreamableHttp.ts

@@ -112,7 +112,11 @@ app.get('/mcp', async (req: Request, res: Response) => {
 
 // Start the server
 const PORT = 3000;
-app.listen(PORT, () => {
+app.listen(PORT, (error) => {
+  if (error) {
+    console.error('Failed to start server:', error);
+    process.exit(1);
+  }
   console.log(`Server listening on port ${PORT}`);
 });