Enable TCP_NODELAY and SCTP_NODELAY by default

- Fixes #939
- Add PlatformDependent.canEnableTcpNoDelayByDefault()
  - Currently returns false on Android. Will change if necessary later.

common/src/main/java/io/netty/util/internal/PlatformDependent.java

@@ -42,6 +42,8 @@ public final class PlatformDependent {
 
     private static final int JAVA_VERSION = javaVersion0();
 
+    private static final boolean CAN_ENABLE_TCP_NODELAY_BY_DEFAULT = !isAndroid();
+
     private static final boolean HAS_UNSAFE = hasUnsafe0();
     private static final boolean CAN_FREE_DIRECT_BUFFER = canFreeDirectBuffer0();
     private static final boolean IS_UNALIGNED = isUnaligned0();
@@ -75,6 +77,13 @@ public final class PlatformDependent {
         return JAVA_VERSION;
     }
 
+    /**
+     * Returns {@code true} if and only if it is fine to enable TCP_NODELAY socket option by default.
+     */
+    public static boolean canEnableTcpNoDelayByDefault() {
+        return CAN_ENABLE_TCP_NODELAY_BY_DEFAULT;
+    }
+
     /**
      * Return {@code true} if {@code sun.misc.Unsafe} was found on the classpath and can be used.
      */

example/src/main/java/io/netty/example/echo/EchoServer.java

@@ -43,7 +43,6 @@ public class EchoServer {
             b.group(new NioEventLoopGroup(), new NioEventLoopGroup())
              .channel(NioServerSocketChannel.class)
              .option(ChannelOption.SO_BACKLOG, 100)
-             .childOption(ChannelOption.TCP_NODELAY, true)
              .handler(new LoggingHandler(LogLevel.INFO))
              .childHandler(new ChannelInitializer<SocketChannel>() {
                  @Override

example/src/main/java/io/netty/example/filetransfer/FileServer.java

@@ -53,7 +53,6 @@ public class FileServer {
             b.group(new NioEventLoopGroup(), new NioEventLoopGroup())
              .channel(NioServerSocketChannel.class)
              .option(ChannelOption.SO_BACKLOG, 100)
-             .childOption(ChannelOption.TCP_NODELAY, true)
              .handler(new LoggingHandler(LogLevel.INFO))
              .childHandler(new ChannelInitializer<SocketChannel>() {
                  @Override

example/src/main/java/io/netty/example/sctp/NioSctpEchoServer.java

@@ -20,7 +20,6 @@ import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.sctp.SctpChannel;
-import io.netty.channel.sctp.SctpChannelOption;
 import io.netty.channel.sctp.nio.NioSctpServerChannel;
 import io.netty.channel.socket.nio.NioEventLoopGroup;
 import io.netty.handler.logging.LogLevel;
@@ -44,7 +43,6 @@ public class NioSctpEchoServer {
             b.group(new NioEventLoopGroup(), new NioEventLoopGroup())
              .channel(NioSctpServerChannel.class)
              .option(ChannelOption.SO_BACKLOG, 100)
-             .childOption(SctpChannelOption.SCTP_NODELAY, true)
              .handler(new LoggingHandler(LogLevel.INFO))
              .childHandler(new ChannelInitializer<SctpChannel>() {
                  @Override

example/src/main/java/io/netty/example/sctp/OioSctpEchoServer.java

@@ -20,7 +20,6 @@ import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.sctp.SctpChannel;
-import io.netty.channel.sctp.SctpChannelOption;
 import io.netty.channel.sctp.oio.OioSctpServerChannel;
 import io.netty.channel.socket.oio.OioEventLoopGroup;
 import io.netty.handler.logging.LogLevel;
@@ -44,7 +43,6 @@ public class OioSctpEchoServer {
             b.group(new OioEventLoopGroup(), new OioEventLoopGroup())
              .channel(OioSctpServerChannel.class)
              .option(ChannelOption.SO_BACKLOG, 100)
-             .childOption(SctpChannelOption.SCTP_NODELAY, true)
              .handler(new LoggingHandler(LogLevel.INFO))
              .childHandler(new ChannelInitializer<SctpChannel>() {
                  @Override

transport-sctp/src/main/java/io/netty/channel/sctp/DefaultSctpChannelConfig.java

@@ -22,6 +22,7 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.channel.ChannelException;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.DefaultChannelConfig;
+import io.netty.util.internal.PlatformDependent;
 
 import java.io.IOException;
 import java.util.Map;
@@ -41,6 +42,15 @@ public class DefaultSctpChannelConfig extends DefaultChannelConfig implements Sc
             throw new NullPointerException("javaChannel");
         }
         this.javaChannel = javaChannel;
+
+        // Enable TCP_NODELAY by default if possible.
+        if (PlatformDependent.canEnableTcpNoDelayByDefault()) {
+            try {
+                setSctpNoDelay(true);
+            } catch (Exception e) {
+                // Ignore.
+            }
+        }
     }
 
     @Override

transport-sctp/src/main/java/io/netty/channel/sctp/SctpChannelConfig.java

@@ -46,13 +46,17 @@ public interface SctpChannelConfig extends ChannelConfig {
 
     /**
      * Gets the <a href="http://openjdk.java.net/projects/sctp/javadoc/com/sun/nio/sctp/SctpStandardSocketOption.html">
-     *     {@code SCTP_NODELAY}</a> option.
+     * {@code SCTP_NODELAY}</a> option.  Please note that the default value of this option is {@code true} unlike the
+     * operating system default ({@code false}). However, for some buggy platforms, such as Android, that shows erratic
+     * behavior with Nagle's algorithm disabled, the default value remains to be {@code false}.
      */
     boolean isSctpNoDelay();
 
     /**
      * Sets the <a href="http://openjdk.java.net/projects/sctp/javadoc/com/sun/nio/sctp/SctpStandardSocketOption.html">
-     *     {@code SCTP_NODELAY}</a> option.
+     * {@code SCTP_NODELAY}</a> option.  Please note that the default value of this option is {@code true} unlike the
+     * operating system default ({@code false}). However, for some buggy platforms, such as Android, that shows erratic
+     * behavior with Nagle's algorithm disabled, the default value remains to be {@code false}.
      */
     SctpChannelConfig setSctpNoDelay(boolean sctpNoDelay);
 

transport/src/main/java/io/netty/channel/socket/DefaultSocketChannelConfig.java

@@ -19,6 +19,7 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.channel.ChannelException;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.DefaultChannelConfig;
+import io.netty.util.internal.PlatformDependent;
 
 import java.net.Socket;
 import java.net.SocketException;
@@ -44,6 +45,15 @@ public class DefaultSocketChannelConfig extends DefaultChannelConfig
             throw new NullPointerException("javaSocket");
         }
         this.javaSocket = javaSocket;
+
+        // Enable TCP_NODELAY by default if possible.
+        if (PlatformDependent.canEnableTcpNoDelayByDefault()) {
+            try {
+                setTcpNoDelay(true);
+            } catch (Exception e) {
+                // Ignore.
+            }
+        }
     }
 
     @Override

transport/src/main/java/io/netty/channel/socket/SocketChannelConfig.java

@@ -19,6 +19,7 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.channel.ChannelConfig;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelOption;
 
 import java.net.Socket;
 import java.net.StandardSocketOptions;
@@ -35,33 +36,39 @@ import java.net.StandardSocketOptions;
  * <tr>
  * <th>Name</th><th>Associated setter method</th>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#SO_KEEPALIVE}</td><td>{@link #setKeepAlive(boolean)}</td>
+ * <td>{@link ChannelOption#SO_KEEPALIVE}</td><td>{@link #setKeepAlive(boolean)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#SO_REUSEADDR}</td><td>{@link #setReuseAddress(boolean)}</td>
+ * <td>{@link ChannelOption#SO_REUSEADDR}</td><td>{@link #setReuseAddress(boolean)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#SO_LINGER}</td><td>{@link #setSoLinger(int)}</td>
+ * <td>{@link ChannelOption#SO_LINGER}</td><td>{@link #setSoLinger(int)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#TCP_NODELAY}</td><td>{@link #setTcpNoDelay(boolean)}</td>
+ * <td>{@link ChannelOption#TCP_NODELAY}</td><td>{@link #setTcpNoDelay(boolean)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#SO_RCVBUF}</td><td>{@link #setReceiveBufferSize(int)}</td>
+ * <td>{@link ChannelOption#SO_RCVBUF}</td><td>{@link #setReceiveBufferSize(int)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#SO_SNDBUF}</td><td>{@link #setSendBufferSize(int)}</td>
+ * <td>{@link ChannelOption#SO_SNDBUF}</td><td>{@link #setSendBufferSize(int)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#IP_TOS}</td><td>{@link #setTrafficClass(int)}</td>
+ * <td>{@link ChannelOption#IP_TOS}</td><td>{@link #setTrafficClass(int)}</td>
  * </tr><tr>
- * <td>{@link io.netty.channel.ChannelOption#ALLOW_HALF_CLOSURE}</td><td>{@link #setAllowHalfClosure(boolean)}</td>
+ * <td>{@link ChannelOption#ALLOW_HALF_CLOSURE}</td><td>{@link #setAllowHalfClosure(boolean)}</td>
  * </tr>
  * </table>
  */
 public interface SocketChannelConfig extends ChannelConfig {
 
     /**
-     * Gets the {@link StandardSocketOptions#TCP_NODELAY} option.
+     * Gets the {@link StandardSocketOptions#TCP_NODELAY} option.  Please note that the default value of this option
+     * is {@code true} unlike the operating system default ({@code false}). However, for some buggy platforms, such as
+     * Android, that shows erratic behavior with Nagle's algorithm disabled, the default value remains to be
+     * {@code false}.
      */
     boolean isTcpNoDelay();
 
     /**
-     * Sets the {@link StandardSocketOptions#TCP_NODELAY} option.
+     * Sets the {@link StandardSocketOptions#TCP_NODELAY} option.  Please note that the default value of this option
+     * is {@code true} unlike the operating system default ({@code false}). However, for some buggy platforms, such as
+     * Android, that shows erratic behavior with Nagle's algorithm disabled, the default value remains to be
+     * {@code false}.
      */
     SocketChannelConfig setTcpNoDelay(boolean tcpNoDelay);
 

transport/src/main/java/io/netty/channel/socket/aio/DefaultAioSocketChannelConfig.java

@@ -19,6 +19,7 @@ import io.netty.buffer.ByteBufAllocator;
 import io.netty.channel.ChannelException;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.DefaultChannelConfig;
+import io.netty.util.internal.PlatformDependent;
 
 import java.io.IOException;
 import java.net.SocketOption;
@@ -57,6 +58,7 @@ final class DefaultAioSocketChannelConfig extends DefaultChannelConfig
      */
     DefaultAioSocketChannelConfig(AioSocketChannel channel) {
         super(channel);
+        enableTcpNoDelay();
     }
 
     /**
@@ -65,6 +67,18 @@ final class DefaultAioSocketChannelConfig extends DefaultChannelConfig
     DefaultAioSocketChannelConfig(AioSocketChannel channel, NetworkChannel javaChannel) {
         super(channel);
         this.javaChannel.set(javaChannel);
+        enableTcpNoDelay();
+    }
+
+    private void enableTcpNoDelay() {
+        // Enable TCP_NODELAY by default if possible.
+        if (PlatformDependent.canEnableTcpNoDelayByDefault()) {
+            try {
+                setTcpNoDelay(true);
+            } catch (Exception e) {
+                // Ignore.
+            }
+        }
     }
 
     @Override