Java netty长时间通讯不了就自动断掉 netty 客户端 长连接

Netty是一个高性能、异步事件驱动的NIO框架，它提供了对TCP、UDP和文件传输的支持。

Netty是对JDK自带的NIO的API进行封装，具有高并发，高性能等优点。

项目中经常用到netty实现服务器与设备的通信，先写服务端代码：

@Slf4j
@Component
public class NettyServerBootstrap {

    private Channel serverChannel;
    private static final int DEFAULT_PORT = 60782;
    //bossGroup只是处理连接请求
    private static EventLoopGroup bossGroup = null;
    //workGroup处理非连接请求，如果牵扯到数据量处理业务非常耗时的可以再单独新建一个eventLoopGroup,并在childHandler初始化的时候添加到pipeline绑定
    private static EventLoopGroup workGroup = null;

    /**
     * 启动Netty服务
     *
     * @return 启动结果
     */
    @PostConstruct
    public boolean start() {
        bossGroup = new NioEventLoopGroup();
        workGroup = new NioEventLoopGroup();
        //创建服务端启动对象
        ServerBootstrap bootstrap = new ServerBootstrap();
        try {
            //使用链式编程来设置
            bootstrap.group(bossGroup, workGroup)//设置两个线程组
                    //使用NioSocketChannel作为服务器的通道实现
                    .channel(NioServerSocketChannel.class)
                    //设置线程队列得到的连接数
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    //设置保持活动连接状态
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    //设置处理器  WorkerGroup 的 EvenLoop 对应的管道设置处理器
                    .childHandler(new ChannelInitializer<Channel>() {

                        @Override
                        protected void initChannel(Channel ch){
                            log.info("--------------有客户端连接");
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new StringEncoder());
                            ch.pipeline().addLast(new NettyServerHandler());
                        }
                    });
            //绑定端口, 同步等待成功;
            ChannelFuture future = bootstrap.bind(DEFAULT_PORT).sync();
            log.info("netty服务启动成功，ip：{}，端口：{}", InetAddress.getLocalHost().getHostAddress(), DEFAULT_PORT);
            serverChannel = future.channel();
            ThreadUtil.execute(() -> {
                //等待服务端监听端口关闭
                try {
                    future.channel().closeFuture().sync();
                    log.info("netty服务正常关闭成功，ip：{}，端口：{}", InetAddress.getLocalHost().getHostAddress(), DEFAULT_PORT);
                } catch (InterruptedException | UnknownHostException e) {
                    e.printStackTrace();
                } finally {
                    shutdown();
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
            log.error("netty服务异常，异常原因：{}", e.getMessage());
            return false;
        }
        return true;
    }


    /**
     * 关闭当前server
     */
    public boolean close() {
        if (serverChannel != null) {
            serverChannel.close();//关闭服务
            try {
                //保险起见
                serverChannel.closeFuture().sync();
            } catch (InterruptedException e) {
                e.printStackTrace();
                return false;
            } finally {
                shutdown();
                serverChannel = null;
            }
        }
        return true;
    }

    /**
     * 优雅关闭
     */
    private void shutdown() {
        workGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();
    }

}

服务端处理类代码：

@Slf4j
public class NettyServerHandler extends SimpleChannelInboundHandler<String> {

    /**
     * 处理读取到的msg
     *
     * @param ctx 上下文
     * @param msg 数据
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx,String msg) throws Exception {
        System.out.println("服务端收到的消息--------"+msg);
        ctx.channel().writeAndFlush("ok");
    }

    /**
     * 断开连接
     *
     * @param ctx 傻瓜下文
     */
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        ChannelId channelId = ctx.channel().id();
        log.info("客户端id:{},断开连接,ip:{}", channelId, ctx.channel().remoteAddress());
        super.handlerRemoved(ctx);
    }

}

接下来模拟客户端：

@Configuration
@Component
public class TianmiaoClient {


    private static String ip;

    private static int port ;

    @Value("${tianmiao.nettyServer.ip}")
    public void setIp(String ip) {
        this.ip = ip;
    }

    @Value("${tianmiao.nettyServer.port}")
    public void setPort(int port) {
        this.port = port;
    }

    /**
     * 服务类
     */
    private static Bootstrap bootstrap=null;

    /**
     * 初始化  项目启动后自动初始化
     */
    @PostConstruct
    public void init() {

        //worker
        EventLoopGroup worker = new NioEventLoopGroup();

        bootstrap = new Bootstrap();
        //设置线程池
        bootstrap.group(worker);

        //设置socket工厂
        bootstrap.channel(NioSocketChannel.class);

        //设置管道
        bootstrap.handler(new ChannelInitializer<Channel>() {

            @Override
            protected void initChannel(Channel ch) throws Exception {
                ch.pipeline().addLast(new StringDecoder());
                ch.pipeline().addLast(new StringEncoder());
                ch.pipeline().addLast(new TianmiaoClientHandler());
            }
        });
    }


    /**
     * 获取会话 （获取或者创建一个会话）
     */
    public Channel createChannel() {
        try {
            Channel channel = bootstrap.connect( ip, port).sync().channel();
            return channel;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}

客户端处理类代码

public class TianmiaoClientHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String s) throws Exception {
        System.out.println("服务端发过来的消息："+s);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(".......................tcp断开连接.........................");
        //移除
        Channel channel = ctx.channel();
        channel.close().sync();
        super.channelInactive(ctx);
    }

}

管理客户端channel的一个工具类：

public class TianmiaoChannelManager {

    /**
     * 在线会话(存储注册成功的会话)
     */
    private static final ConcurrentHashMap<String, Channel> onlineChannels = new ConcurrentHashMap<>();


    /**
     * 加入
     *
     * @param mn
     * @param channel
     * @return
     */
    public static boolean putChannel(String mn, Channel channel) {
        if (!onlineChannels.containsKey(mn)) {
            boolean success = onlineChannels.putIfAbsent(mn, channel) == null ? true : false;
            return success;
        }
        return false;
    }

    /**
     * 移除
     *
     * @param mn
     */
    public static Channel removeChannel(String mn) {
        return onlineChannels.remove(mn);
    }

    /**
     * 获取Channel
     *
     * @param mn
     * @return
     */
    public static Channel getChannel(String mn) {
        // 获取一个可用的会话
        Channel channel = onlineChannels.get(mn);
        if (channel != null) {
            // 连接有可能是断开，加入已经断开连接了，我们需要进行尝试重连
            if (!channel.isActive()) {
                //先移除之前的连接
                removeChannel(mn);
                return null;
            }
        }
        return channel;
    }

    /**
     * 发送消息[自定义协议]
     *
     * @param <T>
     * @param mn
     * @param msg
     */
    public static <T> void sendMessage(String mn, String msg) {
        Channel channel = onlineChannels.get(mn);
        if (channel != null && channel.isActive()) {
            channel.writeAndFlush(msg);
        }
    }

    /**
     * 发送消息[自定义协议]
     *
     * @param <T>
     * @param msg
     */
    public static <T> void sendChannelMessage(Channel channel, String msg) {
        if (channel != null && channel.isActive()) {
            channel.writeAndFlush(msg);
        }
    }

    /**
     * 关闭连接
     *
     * @return
     */
    public static void closeChannel(String mn) {
        onlineChannels.get(mn).close();
    }
}

最后是客户端使用方法：

/**
 * 发送数据包
 * @param key
 */
public static void tianmiaoData(String key, String data) {
    Channel channel = TianmiaoChannelManager.getChannel(key);
    //将通道存入
    if(channel==null){
        TianmiaoClient client = new TianmiaoClient();
        channel = client.createChannel();
        TianmiaoChannelManager.putChannel(key, channel);
    }
    if (channel != null && channel.isActive()) {
        //发送数据
        channel.writeAndFlush(data);
        System.out.println("-------------天苗转发数据成功-------------");
    }
}