初识Netty 一 (基于Netty简单的客户端，服务器连接demo)

绝地灬酷狼 2023-02-12 06:19 153阅读 0赞

> 说明：此demo不考虑粘包和半包情况

[源码][Link 1]

## Netty依赖 ##

<dependency>
                <groupId>io.netty</groupId>
                <artifactId>netty-all</artifactId>
                <version>5.0.0.Alpha1</version>
    </dependency>
    
    
    <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-simple</artifactId>
                <version>1.7.25</version>
    </dependency>
    <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.12</version>
    </dependency>

## 1. 服务器编写 ##

NettyServer

@Slf4j
    public class NettyServer { 
    
        public static void main(String[] args) { 
            int port = 8080;
            // 创建链各个Reactor线程租，一个用于服务端接受客户端连接
            // 一个用于SocketChannel的网络读写
            EventLoopGroup bossGroup = new NioEventLoopGroup();
            EventLoopGroup workerGroup = new NioEventLoopGroup();
            try { 
                // netty 用于启动NIO服务端的辅助启动类，不低降低服务端开发难度
                ServerBootstrap b = new ServerBootstrap();
                b.group(bossGroup, workerGroup)
                        .channel(NioServerSocketChannel.class)
                        .option(ChannelOption.SO_BACKLOG, 1024)//配置NioServerSocketChannel 的TCP 参数
                        .childHandler(new ChildChannelHeandler());// 绑定I/O事件处理类 ChildChannelHeandler
                log.info("服务器启动" + "端口 {}", port);
                // 绑定端口，调用同步阻塞等待成功
                ChannelFuture f = b.bind(port).sync();
                //等待服务端监听端口关闭
                f.channel().closeFuture().sync();
            } catch (InterruptedException e) { 
                e.printStackTrace();
            } finally { 
                bossGroup.shutdownGracefully();
                workerGroup.shutdownGracefully();
    
            }
        }
    
    }
    
    class ChildChannelHeandler extends ChannelInitializer<SocketChannel> { 
    
        @Override
        protected void initChannel(SocketChannel socketChannel) throws Exception { 
            socketChannel.pipeline().addLast(new TimeServerHandler());
        }
    }

TimeServerHandler

/** * @author WH * @version 1.0 * @date 2020/5/24 21:48 * @Description 继承ChannelHandlerAdapter 对网络事件进行读写 */
    @Slf4j
    public class TimeServerHandler extends ChannelHandlerAdapter { 
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception{ 
            System.out.println("111111111111");
            //将msg转换成Netty的ByteBuf对象
            ByteBuf buf = (ByteBuf) msg;
            //buf.readableBytes()获取缓冲区可读的字节数
            byte[] req = new byte[buf.readableBytes()];
            // 将缓冲区的字节数组复制到新的byte数组中
            buf.readBytes(req);
            String body = new String(req, "UTF-8");
            //请求信息
            log.info("客户端请求参数boyd: {}", body);
            String message = "服务端收到了你的消息" + body;
            ByteBuf resp = Unpooled.copiedBuffer(message.getBytes());
            ctx.write(resp);
        }
    
        @Override
        public void channelReadComplete(ChannelHandlerContext ctx) throws Exception{ 
            //将消息发送队列中的消息写入到SocketChannel中发送给客户端
            ctx.flush();
    
        }
    
        // 客户端断开连接监听
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { 
            log.info("客户端断开了连接");
            ctx.close();
        }
    
    }

## 客户端 ##

NettyClient

public class NettyClient { 
    
        public static void main(String[] args) { 
            //配置客户端NIO线程租
            EventLoopGroup group = new NioEventLoopGroup();
            try { 
                Bootstrap b = new Bootstrap();
                b.group(group).channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                .handler(new ChannelInitializer<SocketChannel>() { 
    
                    @Override
                    public void initChannel(SocketChannel ch) throws Exception{ 
                        ch.pipeline().addLast(new TimeClinetHandler());
    
                    }
    
                });
                //发起异步连接操作
                ChannelFuture f = b.connect("127.0.0.1", 8080).sync();
                //等待客户端链路关闭
                f.channel().closeFuture().sync();
            } catch (InterruptedException e) { 
                e.printStackTrace();
            } finally { 
                //优雅退出，释放NIO线程租
                group.shutdownGracefully();
            }
    
        }
    }

TimeClinetHandler

@Slf4j
    public class TimeClinetHandler extends ChannelHandlerAdapter { 
    
        private final ByteBuf firstMessage;
    
        public TimeClinetHandler() { 
            byte[] req = "你好服务器".getBytes();
            firstMessage = Unpooled.buffer(req.length);
            firstMessage.writeBytes(req);
            log.info("发送消息 req: {}", new java.lang.String(req));
        }
    
        //当服务器TCP链路建立成功后，调用 channelActive 方法
        @Override
        public void channelActive(ChannelHandlerContext ctx) { 
            log.info("开始发送消息");
            ctx.writeAndFlush(firstMessage);
        }
    
        //当服务器返回应答消息时，调用 channelRead 方法
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception{ 
            ByteBuf buf = (ByteBuf) msg;
            byte[] req = new byte[buf.readableBytes()];
            buf.readBytes(req);
            String body = new String(req, "UTF-8");
            log.info("服务器返回消息为" + body);
        }
    
        
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { 
            log.warn("发生异常" + cause.getMessage());
            ctx.close();
        }
    
    }

## 运行测试 ##

服务器端  
![在这里插入图片描述][20200524235349967.png]  
客户端启动  
![在这里插入图片描述][20200524235357728.png]

[Link 1]: https://github.com/weihubeats/netty-student
[20200524235349967.png]: https://img-blog.csdnimg.cn/20200524235349967.png
[20200524235357728.png]: https://img-blog.csdnimg.cn/20200524235357728.png