Send NOOP on control socket during file transfers.

defaults/src/main/resources/default.properties

@@ -283,6 +283,9 @@ ftp.ssl.session.cache.size=100
 ftp.timezone.auto=false
 ftp.timezone.default=
 
+# Send NOOP to keep the control socket alive during file transfers
+ftp.controlchannel.keepalive.ms=5000
+
 # Authentication header version
 # s3.signature.version=AWS2
 s3.signature.version=AWS4HMACSHA256

ftp/src/main/java/ch/cyberduck/core/ftp/FTPReadFeature.java

@@ -23,6 +23,7 @@
 import ch.cyberduck.core.features.Read;
 import ch.cyberduck.core.transfer.TransferStatus;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.input.ProxyInputStream;
 import org.apache.commons.net.ftp.FTP;
 import org.apache.commons.net.ftp.FTPReply;
@@ -31,6 +32,8 @@
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.SocketTimeoutException;
+import java.time.Duration;
 import java.util.EnumSet;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -85,12 +88,19 @@ public EnumSet<Flags> features(final Path file) {
     }
 
     private final class ReadReplyInputStream extends ProxyInputStream {
+        private final long idleMillis;
+        private long lastIdleTimeMillis = System.currentTimeMillis();
         private final AtomicBoolean close;
         private final TransferStatus status;
 
         public ReadReplyInputStream(final InputStream proxy, final TransferStatus status) {
+            this(proxy, status, session.getClient().getControlKeepAliveTimeoutDuration());
+        }
+
+        public ReadReplyInputStream(final InputStream proxy, final TransferStatus status, final Duration idleDuration) {
             super(proxy);
             this.status = status;
+            this.idleMillis = idleDuration.toMillis();
             this.close = new AtomicBoolean();
         }
 
@@ -104,8 +114,7 @@ public void close() throws IOException {
                 super.close();
                 if(session.isConnected()) {
                     // Read 226 status after closing stream
-                    int reply = session.getClient().getReply();
-                    if(!FTPReply.isPositiveCompletion(reply)) {
+                    if(!FTPReply.isPositiveCompletion(session.getClient().getReply())) {
                         final String text = session.getClient().getReplyString();
                         if(status.isSegment()) {
                             // Ignore 451 and 426 response because stream was prematurely closed
@@ -125,5 +134,27 @@ else if(!status.isComplete()) {
                 close.set(true);
             }
         }
+
+        @Override
+        protected void afterRead(final int n) throws IOException {
+            if(idleMillis > 0) {
+                if(IOUtils.EOF != n) {
+                    final long nowMillis = System.currentTimeMillis();
+                    if(nowMillis - lastIdleTimeMillis > idleMillis) {
+                        try {
+                            session.getClient().noop();
+                        }
+                        catch(final SocketTimeoutException e) {
+                            log.warn("Timeout waiting for keepalive reply");
+                        }
+                        catch(final IOException e) {
+                            // Ignored
+                        }
+                        lastIdleTimeMillis = nowMillis;
+                    }
+                    super.afterRead(n);
+                }
+            }
+        }
     }
 }

ftp/src/main/java/ch/cyberduck/core/ftp/FTPSession.java

@@ -116,7 +116,7 @@ protected void configure(final FTPClient client) throws IOException {
         client.setDefaultTimeout(timeout);
         client.setDataTimeout(Duration.ofMillis(timeout));
         client.setControlKeepAliveTimeout(Duration.ofMillis(timeout));
-        client.setControlKeepAliveReplyTimeout(Duration.ofMillis(timeout));
+        client.setControlKeepAliveReplyTimeout(Duration.ofMillis(preferences.getInteger("ftp.controlchannel.keepalive.ms")));
         client.setUseEPSVwithIPv4(preferences.getBoolean("ftp.datachannel.epsv"));
         client.setDefaultPort(host.getProtocol().getDefaultPort());
         client.setParserFactory(new FTPParserFactory());

ftp/src/main/java/ch/cyberduck/core/ftp/FTPWriteFeature.java

@@ -31,6 +31,8 @@
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.net.SocketTimeoutException;
+import java.time.Duration;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 public class FTPWriteFeature implements Write<Void> {
@@ -75,13 +77,21 @@ public OutputStream execute() throws BackgroundException {
         }
     }
 
-    public final class ReadReplyOutputStream extends VoidStatusOutputStream {
+    private final class ReadReplyOutputStream extends VoidStatusOutputStream {
+        private final long idleMillis;
+        private long lastIdleTimeMillis = System.currentTimeMillis();
+
         private final AtomicBoolean close;
         private final TransferStatus status;
 
         public ReadReplyOutputStream(final OutputStream proxy, final TransferStatus status) {
+            this(proxy, status, session.getClient().getControlKeepAliveTimeoutDuration());
+        }
+
+        public ReadReplyOutputStream(final OutputStream proxy, final TransferStatus status, final Duration idleDuration) {
             super(proxy);
             this.status = status;
+            this.idleMillis = idleDuration.toMillis();
             this.close = new AtomicBoolean();
         }
 
@@ -115,5 +125,25 @@ else if(!status.isComplete()) {
                 close.set(true);
             }
         }
+
+        @Override
+        protected void afterWrite(final int n) throws IOException {
+            if(idleMillis > 0) {
+                final long nowMillis = System.currentTimeMillis();
+                if(nowMillis - lastIdleTimeMillis > idleMillis) {
+                    try {
+                        session.getClient().noop();
+                    }
+                    catch(final SocketTimeoutException e) {
+                        log.warn("Timeout waiting for keepalive reply");
+                    }
+                    catch(final IOException e) {
+                        // Ignored
+                    }
+                    lastIdleTimeMillis = nowMillis;
+                }
+            }
+            super.afterWrite(n);
+        }
     }
 }