fix(server): handle socket errors on upgrade requests not taken by the HMR server

packages/vite/src/node/server/ws.ts

@@ -231,6 +231,12 @@ export function createWebSocketServer(
         parsedUrl.pathname === hmrBase
       ) {
         handleUpgrade(req, socket as Socket, head, protocol === 'vite-ping')
+      } else {
+        // Node.js detaches its own socket error handler before emitting
+        // `upgrade`, so a socket that no listener takes over would crash the
+        // process when the client resets the connection (e.g. ECONNRESET).
+        // Other listeners (proxy, plugins) still receive the error as usual.
+        socket.on('error', noop)
       }
     }
     wsServer.on('upgrade', hmrServerWsListener)

playground/hmr/__tests__/ws.spec.ts

@@ -0,0 +1,49 @@
+import { errorMonitor } from 'node:events'
+import type { IncomingMessage } from 'node:http'
+import type { Socket } from 'node:net'
+import type { Duplex } from 'node:stream'
+import { expect, test } from 'vitest'
+import WebSocket from 'ws'
+import { isServe, promiseWithResolvers, viteServer, viteTestUrl } from '~utils'
+
+// https://github.com/vitejs/vite/issues/23727
+test.runIf(isServe)(
+  'does not crash when an unhandled upgrade request is reset',
+  async () => {
+    const httpServer = viteServer.httpServer!
+    const upgrade = promiseWithResolvers<Duplex>()
+    const onUpgrade = (request: IncomingMessage, socket: Duplex) => {
+      if (request.url === '/unhandled-upgrade') {
+        upgrade.resolve(socket)
+      }
+    }
+    httpServer.on('upgrade', onUpgrade)
+
+    const wsUrl = new URL('/unhandled-upgrade', viteTestUrl)
+    wsUrl.protocol = 'ws:'
+    let socket: Socket
+    const client = new WebSocket(wsUrl, {
+      finishRequest(request) {
+        request.once('socket', (requestSocket) => {
+          socket = requestSocket
+        })
+        request.end()
+      },
+    })
+    // The connection is deliberately reset before the handshake completes.
+    client.on('error', () => {})
+    try {
+      const serverSocket = await upgrade.promise
+      const socketError = promiseWithResolvers<Error>()
+      serverSocket.once(errorMonitor, socketError.resolve)
+      socket!.resetAndDestroy()
+
+      await expect(socketError.promise).resolves.toMatchObject({
+        code: 'ECONNRESET',
+      })
+    } finally {
+      httpServer.off('upgrade', onUpgrade)
+      client.terminate()
+    }
+  },
+)

playground/hmr/package.json

@@ -10,6 +10,7 @@
     "preview": "vite preview"
   },
   "devDependencies": {
-    "tinyglobby": "^0.2.17"
+    "tinyglobby": "^0.2.17",
+    "ws": "^8.22.0"
   }
 }