netty 客户端与服务端之间通信问题:客户端接收不到数据

问题出现:客户端能够发送消息至服务端，服务端广播的消息在客户端接收不到

Client端

public class ClientChannelInitializer extends ChannelInitializer<SocketChannel> {
    
    
    protected void initChannel(SocketChannel socketChannel) throws Exception {
    
    
        socketChannel.pipeline()
                .addLast(new TankJoinMsgEncoder())  // 客户端通过编码发送至服务端
                .addLast(new TankJoinMsgDecoder())  // 服务端解码服务端广播的消息
                .addLast(new ClientHandler()); 
    }
}

class ClientHandler extends SimpleChannelInboundHandler<TankJoinMsg> {
    
    
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TankJoinMsg msg) throws Exception {
    
    
        if(msg.id.equals(TankFrame.INSTANCE.getMainTank().getId()) ||
                TankFrame.INSTANCE.findByUUID(msg.id)!=null ) return;
        System.out.println(msg);
        Tank t = new Tank(msg);
        TankFrame.INSTANCE.addTank(t);
        ctx.writeAndFlush(new TankJoinMsg(TankFrame.INSTANCE.getMainTank())); // 发送消息至server端
    }
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    
    
        ctx.writeAndFlush(new TankJoinMsg(TankFrame.INSTANCE.getMainTank()));// 会通过TankJoinMsgEncoder编码,编完之后才会写到服务器
    }
}

Server端

public static ChannelGroup clients = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

public void serverStart() {
    
    
        EventLoopGroup bossGroup = new NioEventLoopGroup(1); 
        EventLoopGroup workerGroup = new NioEventLoopGroup(2);

        ServerBootstrap sb = new ServerBootstrap(); // 辅助启动类
        try {
    
    
            ChannelFuture f = sb.group(bossGroup,workerGroup) // 指定线程池组
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
    
    
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
    
    
                            ChannelPipeline pl = socketChannel.pipeline();
                            pl.addLast(new TankJoinMsgDecoder())
                                .addLast(new ServerChildHandler());
                        }
                    })
                    .bind(9999)
                    .sync();
            ServerFrame.INSTANCE.updateServerMsg("server started!");
            f.channel().closeFuture().sync(); // close->ChannelFuture
        } catch (InterruptedException e) {
    
    
            e.printStackTrace();
        }finally {
    
    
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

class ServerChildHandler extends ChannelInboundHandlerAdapter{
    
    
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    
    
        Server.clients.add(ctx.channel());
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    
    
        cause.printStackTrace();
        // 删除出现异常的客户端channel，并关闭连接
        Server.clients.remove(ctx.channel());
        ctx.close();
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    
    
        ServerFrame.INSTANCE.updateClientMsg(msg.toString());
        Server.clients.writeAndFlush(msg);
    }
}

通过一番检查，才发现原因是在Server端下没有增加消息编码，导致Client端无法接收到数据
处理方法:

ChannelFuture f = sb.group(bossGroup,workerGroup) // 指定线程池组
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
    
    
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
    
    
                            ChannelPipeline pl = socketChannel.pipeline();
                            pl.addLast(new TankJoinMsgDecoder())
                                .addLast(new TankJoinMsgEncoder()) // 该位置加上消息编码
                                .addLast(new ServerChildHandler());
                        }
                    })
                    .bind(9999)
                    .sync();