Exception java.nio.channels.ClosedChannelException

Question

I have created a game server using netty 3.5.8. At first, there is not any problem with sending data from server to client. But when server operates for a while, there are many exceptions [java.nio.channels.ClosedChannelException] when I write data to the client channel.

Anyone has gotten this exception before. Is there any tip to fix this? I think about cache buffer cause this.

My code sample like this:

ChannelBuffer bff = ChannelBuffers.buffer(18);
bff.writeByte(Events.S_SERVER_PUSH);  
bff.writeByte((byte)0);
bff.writeInt(idRoom);            
bff.writeInt(playerCnt);
bff.writeInt(gameCnt);
bff.writeInt(freePlayer);
channel.write(bff);

Exception: java.nio.channels.ClosedChannelException

java.nio.channels.ClosedChannelException
        at org.jboss.netty.channel.socket.nio.AbstractNioWorker.cleanUpWriteBuffer(AbstractNioWorker.java:784)
        at org.jboss.netty.channel.socket.nio.AbstractNioWorker.writeFromUserCode(AbstractNioWorker.java:507)
        at org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.handleAcceptedSocket(NioServerSocketPipelineSink.java:129)
        at org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.eventSunk(NioServerSocketPipelineSink.java:66)
        at org.jboss.netty.channel.Channels.write(Channels.java:733)
        at org.jboss.netty.handler.codec.oneone.OneToOneEncoder.doEncode(OneToOneEncoder.java:71)
        at org.jboss.netty.handler.codec.oneone.OneToOneEncoder.handleDownstream(OneToOneEncoder.java:60)
        at org.jboss.netty.channel.Channels.write(Channels.java:712)
        at org.jboss.netty.channel.Channels.write(Channels.java:679)
        at org.jboss.netty.channel.AbstractChannel.write(AbstractChannel.java:248)
       at myclass.SendPushData(GameRoom.java:231)
        at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:296)
        at org.jboss.netty.handler.codec.frame.FrameDecoder.unfoldAndFireMessageReceived(FrameDecoder.java:458)
        at org.jboss.netty.handler.codec.frame.FrameDecoder.callDecode(FrameDecoder.java:439)
        at org.jboss.netty.handler.codec.frame.FrameDecoder.messageReceived(FrameDecoder.java:303)
        at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:268)
        at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:255)
        at org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:84)
        at org.jboss.netty.channel.socket.nio.AbstractNioWorker.processSelectedKeys(AbstractNioWorker.java:471)
        at org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:332)
        at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:35)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)

Answer 1

ClosedChannelException merely tells you that the connection has been closed, so, the write request you issued could not be done. It usually means either:

(1) your application closed the connection somewhere else before you write the message or
(2) your peer closed the connection before reading your message.

If you fix (1) and (2), you should not see the ClosedChannelException anymore.

Answer 2

ClosedChannelException means you have closed the channel and continued to use it. It is a programming error on your part.