Fix NPE in NettyConnectListener

client/src/main/java/org/asynchttpclient/netty/channel/NettyConnectListener.java

@@ -98,7 +98,12 @@ public void onSuccess(Channel channel, InetSocketAddress remoteAddress) {
 
         Request request = future.getTargetRequest();
         Uri uri = request.getUri();
-        timeoutsHolder.setResolvedRemoteAddress(remoteAddress);
+        // don't set a null resolved address - if the remoteAddress is null we keep
+        // the previously scheduled (possibly unresolved) address to avoid NPEs in
+        // timeout logging and keep useful diagnostic information
+        if (remoteAddress != null) {
+            timeoutsHolder.setResolvedRemoteAddress(remoteAddress);
+        }
         ProxyServer proxyServer = future.getProxyServer();
 
         // For HTTPS proxies, establish SSL connection to the proxy server first

client/src/main/java/org/asynchttpclient/netty/timeout/TimeoutTimerTask.java

@@ -57,6 +57,28 @@ public void clean() {
 
     void appendRemoteAddress(StringBuilder sb) {
         InetSocketAddress remoteAddress = timeoutsHolder.remoteAddress();
+
+        // Guard against null remoteAddress which can happen when the TimeoutsHolder
+        // was created without an original remote address (for example when using a
+        // pooled channel whose remoteAddress() returned null). In that case fall
+        // back to the URI host/port from the request to avoid a NPE and provide
+        // a useful diagnostic.
+        if (remoteAddress == null) {
+            if (nettyResponseFuture != null && nettyResponseFuture.getTargetRequest() != null) {
+                try {
+                    String host = nettyResponseFuture.getTargetRequest().getUri().getHost();
+                    int port = nettyResponseFuture.getTargetRequest().getUri().getExplicitPort();
+                    sb.append(host == null ? "unknown" : host);
+                    sb.append(':').append(port);
+                } catch (Exception ignored) {
+                    sb.append("unknown:0");
+                }
+            } else {
+                sb.append("unknown:0");
+            }
+            return;
+        }
+
         sb.append(remoteAddress.getHostString());
         if (!remoteAddress.isUnresolved()) {
             sb.append('/').append(remoteAddress.getAddress().getHostAddress());

client/src/main/java/org/asynchttpclient/netty/timeout/TimeoutsHolder.java

@@ -110,6 +110,12 @@ public void cancel() {
     }
 
     private Timeout newTimeout(TimerTask task, long delay) {
-        return requestSender.isClosed() ? null : nettyTimer.newTimeout(task, delay, TimeUnit.MILLISECONDS);
+        // requestSender or nettyTimer might be null in unit tests or in some edge
+        // cases where a channel's remote address wasn't available. In such cases
+        // avoid scheduling any timeouts rather than throwing a NPE.
+        if (requestSender == null || nettyTimer == null || requestSender.isClosed()) {
+            return null;
+        }
+        return nettyTimer.newTimeout(task, delay, TimeUnit.MILLISECONDS);
     }
 }

client/src/test/java/org/asynchttpclient/netty/timeout/TimeoutTimerTaskTest.java

@@ -0,0 +1,87 @@
+/*
+ *    Copyright (c) 2014-2025 AsyncHttpClient Project. All rights reserved.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.asynchttpclient.netty.timeout;
+
+import org.asynchttpclient.AsyncCompletionHandler;
+import org.asynchttpclient.DefaultAsyncHttpClientConfig;
+import org.asynchttpclient.Request;
+import org.asynchttpclient.RequestBuilder;
+import org.asynchttpclient.channel.ChannelPoolPartitioning;
+import org.asynchttpclient.netty.NettyResponseFuture;
+import org.junit.jupiter.api.Test;
+
+import java.net.InetSocketAddress;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class TimeoutTimerTaskTest {
+
+    @Test
+    public void appendRemoteAddressShouldNotThrowWhenRemoteAddressIsNull() {
+        Request request = new RequestBuilder().setUrl("http://example.com:12345").build();
+        NettyResponseFuture<?> future = new NettyResponseFuture<>(request, new AsyncCompletionHandler<Object>() {
+            @Override
+            public Object onCompleted(org.asynchttpclient.Response response) throws Exception {
+                return null;
+            }
+        }, null,
+                0, ChannelPoolPartitioning.PerHostChannelPoolPartitioning.INSTANCE, null, null);
+
+        // create TimeoutsHolder without an original remote address
+        TimeoutsHolder timeoutsHolder = new TimeoutsHolder(null, future, null, new DefaultAsyncHttpClientConfig.Builder().build(), null);
+
+        TimeoutTimerTask task = new TimeoutTimerTask(future, null, timeoutsHolder) {
+            @Override
+            public void run(io.netty.util.Timeout timeout) {
+                // no-op
+            }
+        };
+
+        StringBuilder sb = new StringBuilder();
+        task.appendRemoteAddress(sb);
+
+        // fallback should include URI host/port
+        assertTrue(sb.toString().contains("example.com:12345"), sb.toString());
+    }
+
+    @Test
+    public void appendRemoteAddressShouldPrintResolvedAddressIfAvailable() {
+        Request request = new RequestBuilder().setUrl("http://example.com:12345").build();
+        NettyResponseFuture<?> future = new NettyResponseFuture<>(request, new AsyncCompletionHandler<Object>() {
+            @Override
+            public Object onCompleted(org.asynchttpclient.Response response) throws Exception {
+                return null;
+            }
+        }, null,
+                0, ChannelPoolPartitioning.PerHostChannelPoolPartitioning.INSTANCE, null, null);
+
+        TimeoutsHolder timeoutsHolder = new TimeoutsHolder(null, future, null, new DefaultAsyncHttpClientConfig.Builder().build(), null);
+
+        // set a resolved remote address
+        timeoutsHolder.setResolvedRemoteAddress(new InetSocketAddress("127.0.0.1", 8080));
+
+        TimeoutTimerTask task = new TimeoutTimerTask(future, null, timeoutsHolder) {
+            @Override
+            public void run(io.netty.util.Timeout timeout) {
+                // no-op
+            }
+        };
+
+        StringBuilder sb = new StringBuilder();
+        task.appendRemoteAddress(sb);
+        assertTrue(sb.toString().contains(":8080"), sb.toString());
+    }
+}