大伙有没有出现过这样的问题。用netty做集群服务器，包括客户端（clientBootstrap）和服务端（serverBootstrap），系统空闲3个多小时候，客户端与服务端的连接会自动断开（“远程主机强迫关闭了一个现有的连接”），系统重新后连接报异常：
java.lang.IllegalArgumentException: promise already done: DefaultChannelPromise@2038329b(failure(java.util.concurrent.CancellationException)
at io.netty.channel.DefaultChannelHandlerContext.validatePromise(DefaultChannelHandlerContext.java:806)
at io.netty.channel.DefaultChannelHandlerContext.connect(DefaultChannelHandlerContext.java:477)
at io.netty.channel.DefaultChannelHandlerContext.connect(DefaultChannelHandlerContext.java:467)
at io.netty.channel.DefaultChannelPipeline.connect(DefaultChannelPipeline.java:847)
at io.netty.channel.AbstractChannel.connect(AbstractChannel.java:199)
at io.netty.bootstrap.Bootstrap$2.run(Bootstrap.java:165)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:354)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:353)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101)
at java.lang.Thread.run(Unknown Source)
最后：
Caused by: java.net.NoRouteToHostException: No route to host: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source)
at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:191)
at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:279)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:461)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:378)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:350)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101)
请问这个问题如何解决，我有做心跳处理，客户端每个几秒会请求服务端，这样都还会自动断开连接，好郁闷....
