首次写入后通道关闭

Question

我写了一个客户端类来处理到不同 TCP 服务器的多个 TCP 连接，如下所示：

    private int nThreads;
    private Charset charset;
    private Bootstrap bootstrap;

    private Map<String, Channel> channels = new HashMap<String, Channel>();

    public MyClass() {
        bootstrap = new Bootstrap()
            .group(new NioEventLoopGroup(nThreads))
            .channel(NioSocketChannel.class)
            .option(ChannelOption.SO_KEEPALIVE, true)
            .handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new StringEncoder(charset));
                }
            });
    }

    public void send(MyObject myObject) {
        final String socket = myobject.getSocket();

        //Check if a channel already exists for this socket
        Channel channel = channels.get(socket);
        if(channel == null) {
            /* No channel found for this socket. */

            //Extract host and port from socket
            String[] hostport = socket.split(":", 2);
            int port = Integer.parseInt(hostport[1]);

            //Create new channel
            ChannelFuture connectionFuture;
            try {
                connectionFuture = bootstrap.connect(hostport[0], port).await();
            } catch (InterruptedException e) {
                return;
            }

            //Connection operation is completed, check status
            if(!connectionFuture.isSuccess()) {
                return;
            }

            //Add channel to the map
            channel = connectionFuture.channel();
            channels.put(notifSocket, channel);
        }

        //Write message on channel
        final String message = myObject.getMessage();
        channel.writeAndFlush(message).addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                if(!future.isSuccess()) {
                    //Log cause
                    return;
                }
            }
        });
    }   
}

当send() 方法为给定的套接字第一次调用时，将建立与远程服务器的连接并正确发送消息。但是，当对同一个socket第二次调用send()方法时，在map中找到了Channel，但是writeAndFlush()操作失败，原因是channel被关闭了。

我在我的代码中没有看到我关闭此Channel 的任何地方。是否有特殊配置可以避免 Netty 关闭Channel？

谢谢， 迈克尔

Answer 1

远程主机可能会在空闲时间过长时关闭通道。您将需要实施某种检测信号以确保通道保持活动状态。