简介

使用Netty与硬件设备通讯，优点，达到百万连接没有任何难度

使用

1.maven依赖

<!--netty所需-->
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.46.Final</version>
</dependency>

2.配置启动服务

在application.yml添加配置

#netty配置
netty:
  enable: true
  server:
    port: 8543

创建启动服务类

/**
 * @author AoDeng
 * @date 2022/8/12
 */
@Component
public class NettyServer {

    private static final Logger log = LoggerFactory.getLogger(NettyServer.class);

    @Value("${netty.server.port}")
    private Integer nettyPort;

    @Value("${netty.enable}")
    private boolean enable;

    @Autowired
    private NettyServerEventHandle nettyEventHandle;

    private EventLoopGroup boss = new NioEventLoopGroup();

    private EventLoopGroup work = new NioEventLoopGroup();

    /**
     * 启动 Netty
     */
    @PostConstruct
    public void start() {
        if (enable) {
            try {
                ServerBootstrap bootstrap = new ServerBootstrap()
                        .group(boss, work)
                        .channel(NioServerSocketChannel.class)
                        .localAddress(new InetSocketAddress(nettyPort))
                        //服务端接受连接的队列长度，如果队列已满，客户端连接将被拒绝
                        .option(ChannelOption.SO_BACKLOG, 128)
                        //Socket参数，连接保活，默认值为False。启用该功能时，TCP会主动探测空闲连接的有效性。
                        //可以将此功能视为TCP的心跳机制，需要注意的是：默认的心跳间隔是7200s即2小时。Netty默认关闭该功能。
                        .childOption(ChannelOption.SO_KEEPALIVE, true)
                        .childHandler(new ChannelInitializer<SocketChannel>() {
                            @Override
                            protected void initChannel(SocketChannel ch) {
                                ch.pipeline()
                                        .addLast(new IdleStateHandler(60, 60, 20, TimeUnit.SECONDS))
                                        .addLast(nettyEventHandle);
                            }
                        });
                //绑定并开始接受传入的连接。
                ChannelFuture future = bootstrap.bind().sync();
                if (future.isSuccess()) {
                    log.info("Start Netty Serve Success..");
                }
            } catch (Exception e) {
                log.error("启动Netty服务异常,异常原因:{}", e.getMessage());
            }
        }
    }

    /**
     * 销毁
     */
    @PreDestroy
    public void destroy() {
        boss.shutdownGracefully().syncUninterruptibly();
        work.shutdownGracefully().syncUninterruptibly();
        log.info("Close Netty Serve Success..");
    }
}

3.事件监听，业务处理

在channelRead方法中，接收消息，处理相关业务即可

/**
 * @author AoDeng
 * @date 2022/8/12
 */
@Component
@ChannelHandler.Sharable
public class NettyServerEventHandle extends ChannelInboundHandlerAdapter {

    private static final Logger log = LoggerFactory.getLogger(NettyServerEventHandle.class);

    /**
     * 事件监听
     */
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        //获取当前信道状态
        IdleStateEvent event = (IdleStateEvent) evt;
        //连接客户端ID
        String channelId = ctx.channel().id().toString();
        switch (event.state()) {
            //读空闲
            case READER_IDLE:
                break;
            //写空闲
            case WRITER_IDLE:
                break;
            //读写空闲
            case ALL_IDLE:
                log.info("服务端向客户端ID:{}发送心跳数据..", channelId);
                ctx.writeAndFlush(MessageUtil.sendMessage(JSONObject.toJSONString(NettyConfig.SEND_HEAR_MESSAGE)));
                break;
            default:
                break;
        }
        super.userEventTriggered(ctx, evt);
    }

    /**
     * 接收到消息的时候触发
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        try {
            //消息体
            String info = MessageUtil.getMessage(msg);
            //连接客户端ID
            String channelId = ctx.channel().id().toString();
            log.info("（处理前）收到ID:{}发来的消息:{}", channelId, info+" : "+info.length());

            //TODO 消息体根据具体业务处理转换...

            log.info("（处理后）收到客户端ID:{}发来的消息:{}", channelId, info+" : "+info.length());
            //处理业务开始...

            //TODO 收到消息后处理具体业务...

        } catch (Exception e) {
            log.error(e.getMessage(),e);
            ctx.writeAndFlush(MessageUtil.sendMessage(JSONObject.toJSONString(NettyConfig.RESPONSE_ERROR_MESSAGE)));
        }
    }


    /**
     * 绑定
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        //获取客户端IP地址进行身份验证
        String ipAddress = ctx.channel().remoteAddress().toString();
        String channelId = ctx.channel().id().toString();
        log.info("客户端ID:{},IP地址:{}已经成功连接....", channelId, ipAddress);
    }

    /**
     * 取消绑定
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) {

    }

    /**
     * 抛出异常的时候触发
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        String channelId = ctx.channel().id().toString();
        String ipAddress = ctx.channel().remoteAddress().toString();
        log.error("客户端ID:{},IP地址:{}发生了异常....", channelId, ipAddress);
        super.exceptionCaught(ctx, cause);
    }
}

消息编码工具

/**
 * @author AoDeng
 * @date 2022/8/12
 */
public class MessageUtil {
    /**
     * 发送消息编码
     *
     * @param message 消息体
     * @return 编码之后的消息
     */
    public static ByteBuf sendMessage(String message) {
        return Unpooled.wrappedBuffer((message).getBytes((CharsetUtil.UTF_8)));
    }

    /**
     * 接收消息编码
     *
     * @param message 消息体
     * @return 解码之后的消息
     */
    public static String getMessage(Object message) {
        return ((ByteBuf) message).toString(CharsetUtil.UTF_8);
    }
}

常量

/**
 * @author AoDeng
 * @date 2022/8/12
 */
public class NettyConfig {
    public static final String SEND_HEAR_MESSAGE = "服务器发送心跳数据..";

    public static final String RESPONSE_HEAR_MESSAGE = "服务器收到客户端响应数据..";

    public static final String RESPONSE_ERROR_MESSAGE = "服务器处理消息错误,请稍等重试..";
}

测试运行

启动项目，下载个tcp工具，访问127.0.0.1:8543 即可模拟通讯

源码

https://github.com/java-aodeng/demo-netty-20220812