【Netty】Socket 编程(C/S)：基于Netty的Server、Client示例（简单注释）

红太狼 2023-01-01 01:56 243阅读 0赞

首先引入 Netty 的依赖

<dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-all</artifactId>
         <version>4.1.36.Final</version>
    </dependency>

### Server ###

public class NettyServer {
        
        public static void main(String[] args) {
        
            EventLoopGroup bossGroup = new NioEventLoopGroup();
            EventLoopGroup workGroup = new NioEventLoopGroup();
    
            try {
        
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                
                serverBootstrap.group(bossGroup,workGroup)
                        .channel(NioServerSocketChannel.class)
                        .childHandler(new NettyServerInitailizer())
                        .option(ChannelOption.SO_BACKLOG, 128);
    
                ChannelFuture channelFuture = serverBootstrap.bind(8000).sync();
                System.out.println("Netty Server started...");
    
                channelFuture.channel().closeFuture().sync();
            } catch (Exception e){
        
                e.printStackTrace();
            } finally {
        
                bossGroup.shutdownGracefully();
                workGroup.shutdownGracefully();
            }
        }
    
    }

public class NettyServerInitailizer extends ChannelInitializer<SocketChannel> {
        
        @Override
        protected void initChannel(SocketChannel socketChannel) {
        
            ChannelPipeline pipeline = socketChannel.pipeline();
    //        pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
    //        pipeline.addLast(new LengthFieldPrepender(4));
            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
            pipeline.addLast(new NettyServerHandler());
        }
    }

/**
    * SimpleChannelInboundHandler 是 ChannelInboundHandlerAdapter 的子类
    */
    public class NettyServerHandler extends SimpleChannelInboundHandler<String> {
        
    	
    	/**
         * 有新的客户端连接时触发
         *
         * @param ctx 上下文对象, 含有通道channel，管道pipeline
         * @throws Exception
         */
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
        
            System.out.println("新的客户端..." + ctx.channel().remoteAddress());
        }
    	
    	/**
         * 读取客户端发送的数据
         *
         * @param ctx 上下文对象, 含有通道channel，管道pipeline
         * @param msg 就是客户端发送的数据
         * @throws Exception
         */
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        
        	// 注：因为已经引入了编解码器，所以这里直接就是可以读写 String 类型消息，不用再先包装成 ByteBuf
            System.out.println(ctx.channel().remoteAddress() +"：" + msg);
            ctx.channel().writeAndFlush("Hello Client --"+ UUID.randomUUID().toString().substring(0,7));
        }
        
        /**
         * 处理异常, 一般是需要关闭通道
         *
         * @param ctx
         * @param cause
         * @throws Exception
         */
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        
            cause.printStackTrace();
            ctx.close();
        }
    }

### Client ###

public class NettyClient {
        
        public static void main(String[] args){
        
            EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
            
            try {
        
                Bootstrap bootstrap = new Bootstrap();
                bootstrap.group(eventLoopGroup)
                        .channel(NioSocketChannel.class)
                        .handler(new NettyClientInitailizer())
    					
                ChannelFuture channelFuture = bootstrap.connect("localhost",8000).sync();
                System.out.println("Netty Client started...");
    
                channelFuture.channel().closeFuture().sync();
            } catch (Exception e){
        
                e.printStackTrace();
            }
            finally {
        
                eventLoopGroup.shutdownGracefully();
            }
        }
    }

public class NettyClientInitailizer extends ChannelInitializer<SocketChannel> {
        
        @Override
        protected void initChannel(SocketChannel socketChannel) throws Exception {
        
            ChannelPipeline pipeline = socketChannel.pipeline();
    //        pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
    //        pipeline.addLast(new LengthFieldPrepender(4));
            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
            pipeline.addLast(new NettyClientHandler());
        }
    }

public class NettyClientHandler extends SimpleChannelInboundHandler<String> {
        
    	
    	/**
         * 当客户端连接服务器完成就会触发该方法
         *
         * @param ctx
         * @throws Exception
         */
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
        
            System.out.println("成功连接到服务端..." + ctx.channel().remoteAddress());
            // 注：因为已经引入了编解码器，所以这里直接就是可以读写 String 类型消息，不用再先包装成 ByteBuf
            ctx.writeAndFlush("Hello Server！");
        }
    	
    	/**
         * 当通道有读取事件时会触发，即服务端发送数据给客户端
         *
         * @param ctx 上下文对象, 含有通道channel，管道pipeline
         * @param msg 就是客户端发送的数据
         * @throws Exception
         */
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        
            System.out.println("Server："+ msg);
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        
            cause.printStackTrace();
            ctx.close();
        }
    }

先后启动 Server 和 Client，结果如下：

![在这里插入图片描述][20201230163550553.png_pic_center]  
![在这里插入图片描述][20201230163606950.png_pic_center]

[20201230163550553.png_pic_center]: /images/20221120/4617dc386b5a4907bf80b85e3a5751f7.png
[20201230163606950.png_pic_center]: /images/20221120/cd0eba6764a141f58c301eea3e2753d4.png