netty 客户端无法正常关闭

Question

使用netty编写的TCP程序，分为client、server、cli三个部分，希望cli与server连接后发送一段数据并收到回复即退出，但是现在cli可以正常收到回复，却无法正常关闭cli程序

cli启动程序

    public void run (SimpleChannelInboundHandler handler) {
        EventLoopGroup worker = new NioEventLoopGroup(1);

        try{
            Bootstrap b = new Bootstrap();
            b.group(worker)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.SO_KEEPALIVE,true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline()
                                    .addLast("logger",new LoggingHandler(LogLevel.DEBUG))
                                    .addLast(new ProtobufVarint32FrameDecoder())
                                    .addLast(new ProtobufDecoder(Messages.msg.getDefaultInstance()))
                                    .addLast(new ProtobufVarint32LengthFieldPrepender())
                                    .addLast(new ProtobufEncoder())
                                    .addLast(handler);
                        }
                    });

            ChannelFuture future = b.connect(host,port).sync();
            System.out.println("connect complete");
            future.channel().closeFuture().sync();
            System.out.println("channel closed");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            System.out.println("working shutdown");
            final Future f = worker.shutdownGracefully();
            f.addListener(future->{
                if(f == future)
                    System.out.println("closed");
                else{
                    System.out.println("cannot close");
                }
            });
        }
    }

clihandler

public class CliInBoundHandler extends SimpleChannelInboundHandler<Messages.msg> {
    private final static InternalLogger logger = InternalLoggerFactory.getInstance("cli");
    protected List<String> commands;
    private final static int batch_num = 3;
    private int counter = 0;

    public CliInBoundHandler(List<String> commands) {
        this.commands = commands;
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Messages.msg msg) throws Exception {
        logger.info("receive a msg from {} \n {}",ctx.channel().remoteAddress(),msg);
        if(msg.getType() != Messages.msg.Type.RESPONSE){
            System.err.println("invalid response");
        }
        System.out.println(msg.getResponse().getResponse());
        counter ++;
        if(counter == commands.size()){
            System.out.println("try to close ctx");
            ChannelFuture f = ctx.close();
            f.addListener(future -> {
                if(f==future){
                    System.out.println("channel closed in ctx");
                }else{
                    System.out.println("cannot close in ctx");
                }
            });

        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        // auth
        Messages.Auth auth = Messages.Auth.newBuilder().setAuth(Messages.Auth.Type.cli).build();
        final ChannelFuture future = ctx.writeAndFlush(Messages.msg.newBuilder().
                setType(Messages.msg.Type.AUTH).setAuth(auth).build());
        future.sync();


        for(int i=0;i<commands.size();i+=batch_num){
            int to = Math.min(i+batch_num,commands.size());
            Messages.Cmd com = Messages.Cmd.newBuilder().addAllCmds(commands.subList(i,to)).build();
            Messages.msg msg = Messages.msg.newBuilder()
                    .setType(Messages.msg.Type.CMD)
                    .setCmd(com).build();
            ctx.writeAndFlush(msg);
        }
        super.channelActive(ctx);
    }
}

这是cli运行的截图，可以看到所有的debug信息都是正常打印出来的，但是不知道还有哪个线程没有正常停止。尝试用jconsole看过，但是没有看出是哪个线程，而且打开jconsole过一会儿程序就莫名又停止了，但是如果不打开jconsole却一直停止不了。