Netty：使用“IdleStateHandler”来检测断开连接

Question

我阅读了我的服务器的文档IdleStateHandler，并从我的服务器中实现了它，但我不明白如何准确判断客户端是否断开连接，例如客户端失去了 Wifi 连接。

根据我的理解，在我的 Handler 内部，channelInactive()当客户端断开连接时会触发该方法，然后使用IdleStateHandler，IdleState.READER_IDLE当在指定的时间段内没有执行读取时将触发该方法，然后在 3 秒内没有从客户端读取时我关闭了该方法频道并期望会channelInactive被触发，但事实并非如此，为什么？

初始化器

public class ServerInitializer extends ChannelInitializer<SocketChannel> {

    String TAG = "LOG: ";
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        System.out.println(TAG + "Starting ServerInitializer class...");
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("decoder", new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
        pipeline.addLast("encoder", new ObjectEncoder());
        pipeline.addLast("idleStateHandler", new IdleStateHandler(6, 3, 0, TimeUnit.SECONDS));
        pipeline.addLast("handler", new ServerHandler());
    }
}

处理程序

public class ServerHandler extends ChannelInboundHandlerAdapter {

    private String TAG = "LOG: ";

    public ServerHandler(){}

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        Log.w(TAG,"New Client become connected, Sending a message to the Client. Client Socket is: " + ctx.channel().remoteAddress().toString());

        List<String> msg = new ArrayList<>();
        msg.add(0,"sample message 1");
        msg.add(1,"sample message 2");
        sendMessage(ctx, msg);
    }

    public void sendMessage(ChannelHandlerContext ctx, List message){
        ctx.write(message);
        ctx.flush();
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) {
        Log.w(TAG,"A Client become disconnected. Client Socket is: " + ctx.channel().remoteAddress().toString() + " id: " + (String.valueOf(ctx.channel().hashCode())));
         //COnnection id dead, do something here...
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object object) { // (2)
        Log.w(TAG, "CLIENT: "+ ctx.channel().remoteAddress().toString() + " SAYS: " + object);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // (4)
        // Close the connection for that client  when an exception is raised.
        Log.e(TAG,"Something's wrong, CLIENT: "+ ctx.channel().remoteAddress().toString() + " CAUSE: " + cause.toString());
        ctx.close();
    }


    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        Log.w(TAG,"LOLO");
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent e = (IdleStateEvent) evt;
            if (e.state() == IdleState.READER_IDLE) {

                ctx.close(); //Closed the Channel so that the `channelInactive` will be trigger

            } else if (e.state() == IdleState.WRITER_IDLE) {

                ctx.writeAndFlush("ping\n"); //Send ping to client

            }
        }

    }
}

任何人都可以帮助我

Answer 1

IdleStateHandler应该始终是管道中的第一个处理程序。