fix: allow binding when strictPort is set but wildcard port is in use (#22150)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: sapphi-red <49056869+sapphi-red@users.noreply.github.com>

Author: Copilot

packages/vite/src/node/__tests__/http.spec.ts

@@ -213,4 +213,42 @@ describe('port detection', () => {
       `Port ${BASE_PORT} is already in use`,
     )
   })
+
+  test('allows binding to specific host with strictPort when wildcard port is in use', async () => {
+    await using _wildcardServer = await createSimpleServer(BASE_PORT, '0.0.0.0')
+
+    const warnMessages: string[] = []
+    viteServer = await createServer({
+      root: import.meta.dirname,
+      customLogger: {
+        info: () => {},
+        warn: (msg) => warnMessages.push(msg),
+        warnOnce: () => {},
+        error: () => {},
+        clearScreen: () => {},
+        hasErrorLogged: () => false,
+        hasWarned: false,
+      },
+      server: {
+        port: BASE_PORT,
+        host: '127.0.0.1',
+        strictPort: true,
+        ws: false,
+      },
+    })
+
+    try {
+      await viteServer.listen()
+    } catch (e) {
+      // it may not be allowed to bind to specific host when wildcard port is in use
+      expect(() => {
+        throw e
+      }).toThrow(`Port ${BASE_PORT} is already in use`)
+      return
+    }
+
+    const address = viteServer.httpServer!.address()
+    expect(address).toStrictEqual(expect.objectContaining({ port: BASE_PORT }))
+    expect(warnMessages).toContainEqual(expect.stringContaining('wildcard'))
+  })
 })

packages/vite/src/node/http.ts

@@ -229,20 +229,38 @@ export async function httpServerStart(
   for (let port = startPort; port <= MAX_PORT; port++) {
     // Pre-check port availability on wildcard addresses (0.0.0.0, ::)
     // so that we avoid conflicts with other servers listening on all interfaces
-    if (await isPortAvailable(port)) {
+    const portAvailableOnWildcard = await isPortAvailable(port)
+
+    // If port is not available on a wildcard address but strictPort is set,
+    // we still try binding directly before giving up.
+    if (strictPort) {
       const result = await tryBindServer(httpServer, port, host)
       if (result.success) {
+        if (!portAvailableOnWildcard) {
+          logger.warn(
+            colors.yellow(
+              `Port ${port} is in use on a wildcard address, but ${host ?? 'localhost'}:${port} is available. ` +
+                `There may be another server running on a wildcard IP on port ${port}.`,
+            ),
+          )
+        }
         return port
       }
       if (result.error.code !== 'EADDRINUSE') {
         throw result.error
       }
-    }
-
-    if (strictPort) {
       throw new Error(`Port ${port} is already in use`)
     }
 
+    if (portAvailableOnWildcard) {
+      const result = await tryBindServer(httpServer, port, host)
+      if (result.success) {
+        return port
+      }
+      if (result.error.code !== 'EADDRINUSE') {
+        throw result.error
+      }
+    }
     logger.info(`Port ${port} is in use, trying another one...`)
   }
   throw new Error(