Netty服务器消息未发送到客户端

Question

I am trying out netty but it looks like the client does not get my messages when I respond. I wrote the same code using Java NIO and socketChannel and it seems fine. I say this because the client logs whatever I am sending in it logs. Below is my server

public class Server{

    public void init(final int port){

    EventLoopGroup bossGroup = new NioEventLoopGroup(1);  
    EventLoopGroup workerGroup = new NioEventLoopGroup(); 

    try {

        ServerBootstrap bootstrap = new ServerBootstrap();
        bootstrap.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_REUSEADDR, true)
                .handler(new LoggingHandler(LogLevel.INFO))
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    public void initChannel(SocketChannel ch) {
                        ChannelPipeline p = ch.pipeline();
                        p.addLast(new ServerHandler());
                    }
                })

                .option(ChannelOption.SO_BACKLOG, 128)
                .childOption(ChannelOption.SO_KEEPALIVE, true);

        ChannelFuture f = bootstrap.bind("localhost", port).sync(); 

        f.channel().closeFuture().sync(); 

    } catch (InterruptedException e) {
        System.out.println("Server encountered an InterruptedException");
        e.printStackTrace();

    } finally {
        workerGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();
    }
}

Below is my server handler

public class ServerHandler extends ChannelInboundHandlerAdapter {

public static Logger LOG =  LoggerFactory.getLogger(UTPServerHandler.class);
final int LEN = 1028;
private ByteBuf byteBuf;
private MyDecoder myDecoder;

@Override
public void handlerAdded(ChannelHandlerContext ctx) {
    byteBuf     = ctx.alloc().buffer(MAX_PACKET_LENGTH);
    myDecoder = new MyDecoder();
}

@Override
public void handlerRemoved(ChannelHandlerContext ctx) {
    byteBuf.release();
    byteBuf = null;
}

@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {

    byteBuf = (ByteBuf) msg;
    myDecoder.decodeMessage(byteBuf, ctx); //This is where I try to decode which message and respond. I pass ctx along so I know which to reponsd to. See sample response below
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
    cause.printStackTrace();
    System.out.println"Got an exception...");
    ctx.close();
}

}

sample respond:

 public static void dummyResponse(ChannelHandlerContext ctx, int test){

    ByteBuf response = Unpooled.buffer(32);
    response.writeByte(test);
    response.writeByte(test);
    response.writeByte(test);
    response.writeByte(test);
    response.writeByte(test);      
    ctx.channel().writeAndFlush(response);
}

I am doing a tcpdump on my box and I see what I'm sending on the wire so I'm not sure what I'm doing wrong. Also, after a few minutes, this is logged and I'm not sure what I'm doing in my server or server handler to make complain about this:

`2016-10-25 16:58:38.974 [ nioEventLoopGroup-3-1] | ERROR | LEAK: ByteBuf.release() was not called before it's garbage-collected. Enable advanced leak reporting to find out where the leak occurred. To enable advanced leak reporting, specify the JVM option '-Dio.netty.leakDetection.level=advanced' or call ResourceLeakDetector.setLevel() See http://netty.io/wiki/reference-counted-objects.html for more information.

Please any help or suggestion will do. Thanks in advance `

Answer 1

You get a message about release because you allocate a ByteBuf and assign it to byteBuf in your handlerAdded method, then in channelRead you assign byteBuf to your incoming message, causing that first one to be garbage collected without ever being released. Fix this by not allocating it in handlerAdded.