netty服务端实现心跳超时的主动拆链

一、服务器启动示例：

public class MySocketServer {
    protected static Logger logger = LoggerFactory.getLogger(MySocketServer.class);
 
    public void start(int port) {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new SocketServerInitializer());
 
            logger.debug("server side socket start successful on port {}", port);
 
            b.bind(port).sync().channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
            logger.error("{}", e.getMessage());
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

二、各种业务Handler：

public class SocketServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ch.pipeline()
            .addLast(new IdleStateHandler(10, 0, 0, TimeUnit.SECONDS)) // 构造一个超时event消息
            .addLast(new IdleStateTrigger()) // 处理超时event消息
            .addLast(new StringDecoder())
            .addLast(new StringEncoder())
            .addLast(new ServerHandler());
    }
}

三、读空闲（超过10s）的事件处理

public class IdleStateTrigger extends ChannelInboundHandlerAdapter {
    protected static Logger logger = LoggerFactory.getLogger(IdleStateTrigger.class);
 
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleState state = ((IdleStateEvent) evt).state();
            logger.debug("state is {}", state.name());
            if (state == IdleState.READER_IDLE) {
                ctx.close(); // 如果是超过10s没有读到数据，关闭客户端连接
                throw new Exception("idle exception");
            }
        } else {
            super.userEventTriggered(ctx, evt);
        }
    }
 
}

附录、超时功能的快捷实现
使用自带的ReadTimeoutHandler

public class SocketServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
         ch.pipeline()
        .addLast(new StringDecoder())
        .addLast(new StringEncoder())
        .addLast(new ReadTimeoutHandler(10, TimeUnit.SECONDS))
        .addLast(new ServerHandler());
    }
}