From 5229ac7e5882cbfbdeb5aecbb9f199f770776cf1 Mon Sep 17 00:00:00 2001
From: Andy Wilkinson <andy.wilkinson@broadcom.com>
Date: Tue, 11 Nov 2025 16:07:35 +0000
Subject: [PATCH] Stop throwing PortInUseException for unassignable address

Previously, an unassignable address would result in NettyWebServer
incorrectly throwing a PortInUseException.

Fixes gh-47618
---
 .../boot/web/embedded/netty/NettyWebServer.java     |  2 +-
 .../netty/NettyReactiveWebServerFactoryTests.java   | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/netty/NettyWebServer.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/netty/NettyWebServer.java
index 236c7b39929..61180e9f5f6 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/netty/NettyWebServer.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/netty/NettyWebServer.java
@@ -117,7 +117,7 @@ public class NettyWebServer implements WebServer {
 			catch (Exception ex) {
 				PortInUseException.ifCausedBy(ex, ChannelBindException.class, (bindException) -> {
 					if (bindException.localPort() > 0 && !isPermissionDenied(bindException.getCause())) {
-						throw new PortInUseException(bindException.localPort(), ex);
+						PortInUseException.throwIfPortBindingException(bindException, bindException::localPort);
 					}
 				});
 				throw new WebServerException("Unable to start Netty", ex);
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/netty/NettyReactiveWebServerFactoryTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/netty/NettyReactiveWebServerFactoryTests.java
index cb03e6efb0e..fa09e787b6b 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/netty/NettyReactiveWebServerFactoryTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/netty/NettyReactiveWebServerFactoryTests.java
@@ -17,7 +17,9 @@
 package org.springframework.boot.web.embedded.netty;
 
 import java.net.ConnectException;
+import java.net.InetAddress;
 import java.net.SocketAddress;
+import java.net.UnknownHostException;
 import java.time.Duration;
 import java.util.Arrays;
 
@@ -45,6 +47,7 @@ import org.springframework.boot.web.reactive.server.AbstractReactiveWebServerFac
 import org.springframework.boot.web.server.PortInUseException;
 import org.springframework.boot.web.server.Shutdown;
 import org.springframework.boot.web.server.Ssl;
+import org.springframework.boot.web.server.WebServerException;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.ReactorResourceFactory;
 import org.springframework.http.client.reactive.ReactorClientHttpConnector;
@@ -70,7 +73,7 @@ import static org.mockito.Mockito.mock;
 class NettyReactiveWebServerFactoryTests extends AbstractReactiveWebServerFactoryTests {
 
 	@Test
-	void exceptionIsThrownWhenPortIsAlreadyInUse() {
+	void portInUseExceptionIsThrownWhenPortIsAlreadyInUse() {
 		AbstractReactiveWebServerFactory factory = getFactory();
 		factory.setPort(0);
 		this.webServer = factory.getWebServer(new EchoHandler());
@@ -81,6 +84,14 @@ class NettyReactiveWebServerFactoryTests extends AbstractReactiveWebServerFactor
 			.withCauseInstanceOf(Throwable.class);
 	}
 
+	@Test
+	void webServerExceptionIsThrownWhenAddressCannotBeAssigned() throws UnknownHostException {
+		AbstractReactiveWebServerFactory factory = getFactory();
+		factory.setPort(8080);
+		factory.setAddress(InetAddress.getByName("1.2.3.4"));
+		assertThatExceptionOfType(WebServerException.class).isThrownBy(factory.getWebServer(new EchoHandler())::start);
+	}
+
 	@Test
 	void getPortWhenDisposableServerPortOperationIsUnsupportedReturnsMinusOne() {
 		NettyReactiveWebServerFactory factory = new NoPortNettyReactiveWebServerFactory(0);