Netty - The async event-driven network application framework

ByteBuf buf = ...;
buf.writeInt(1).writeBytes(data).writeBoolean(true)...

void channelRegistered(...) throws Exception;
void channelUnregistered(C...) throws Exception;
void channelActive(...) throws Exception;
void channelInactive(...) throws Exception;
void channelRead(...) throws Exception;
void channelReadComplete(...) throws Exception;
void userEventTriggered(...) throws Exception;
void channelWritabilityChanged(...) throws Exception;
void exceptionCaught(...) throws Exception;

void bind(..., ChannelPromise promise) throws Exception;
void connect(..., ChannelPromise promise) throws Exception;
void disconnect(..., ChannelPromise promise) throws Exception;
void close(..., ChannelPromise promise) throws Exception;
void deregister(..., ChannelPromise promise) throws Exception;
void read(...) throws Exception;
void write(..., ChannelPromise promise) throws Exception;
void flush(...) throws Exception;

@Sharable
public class EchoHandler extends ChannelInboundHandlerAdapter {
  @Override
  public void channelRead(ChannelHandlerContext ctx, Object msg) { (1)
    ctx.writeAndFlush(msg);
  }

  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { (2)
    cause.printStacktrace();
    ctx.close();
  }
}

public class ByteToMessageDecoderImpl extends ByteToMessageDecoder {
  @Override
  public void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { }
}

public class MessageToMessageDecoderImpl extends ByteToMessageDecoder<Pojo> {
  @Override
  public void decode(ChannelHandlerContext ctx, Pojo in, List<Object> out) { }
}

public class MessageToByteEncoderImpl extends MessageToByteEncoder<Pojo> {
  @Override
  public void encode(ChannelHandlerContext ctx, Pojo in, ByteBuf out) { }
}

public class MessageToMessageEncoderImpl extends MessageToMessageEncoder<Pojo> {
  @Override
  public void encode(ChannelHandlerContext ctx, Pojo in, List<Object> out) { }
}

$ echo "Netty is shit...." | sed -e 's/is /is the /'
                    Netty is the shit....

Channel ch = ...;
ChannelPipeline p = ch.pipeline();
EventExecutor e1 = new DefaultEventExecutor(16);
EventExecutor e2 = new DefaultEventExecutor(8);

p.addLast(new MyProtocolCodec()); (1)
p.addLast(e1, new MyDatabaseAccessingHandler()); (2)
p.addLast(e2, new MyHardDiskAccessingHandler()); (3)

public class WriteTimeOutHandler extends ChannelOutboundHandlerAdapter {
  @Override
  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
    ctx.write(msg, promise);

    if (!promise.isDone() {
      ctx.executor().schedule(new WriteTimeoutTask(promise), 30, TimeUnit.SECONDS); (1)
    }
  }
}

ServerBootstrap b = new ServerBootstrap();
EventLoopGroup group = new NioEventLoopGroup(numThreads);
try {
  b.group(group, group)
      .channel(NioServerSocketChannel.class)
      .localAddress(new InetSocketAddress(25))
      .childHandler(new ChannelInitializer<SocketChannel>() {
          @Override
          public void initChannel(SocketChannel ch) {
            ch.pipeline().addLast(new YourChannelHandler());
          }
      });
  ChannelFuture f = b.bind().sync();
  f.channel().closeFuture().sync();
} finally {
  group.shutdownGracefully();
}

Bootstrap b = new Bootstrap();
EventLoopGroup group = new NioEventLoopGroup(numThreads);
try {
  b.group(group)
      .channel(NioSocketChannel.class)
      .remoteAddress(new InetSocketAddress("10.0.0.1", 25))
      .handler(new ChannelInitializer<SocketChannel>() {
        @Override
        public void initChannel(SocketChannel ch) {
          ch.pipeline().addLast(new YourChannelHandler());
        }
      });
  ChannelFuture f = b.connect().sync();
  f.channel().closeFuture().sync();
} finally {
  group.shutdownGracefully();
}