Best way to detect unnoticed disconnection?

[IanS]

I need to be able to detect disconnection, such as when a network connection
gets dropped.  I'm using TCP and keepalive, which I thought would detect
this, but it does not appear to.

So I am using an IdleStateHandler along with
channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) to send a ping
message every 15 seconds, and I use the read timer to close the connection
if I haven't received any responses for 30 seconds.  

public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) 
{
	if(e.getState()==IdleState.READER_IDLE)
	{
		// Close the channel.
		if(e.getChannel().isConnected())
			e.getChannel().close();
	}
	else if(e.getState()==IdleState.WRITER_IDLE)
	{
		Message message = Message.newBuilder().setPing(
			Protocol.Ping.newBuilder()
			.setRequest(true)
			.setTimestamp(System.currentTimeMillis())
			.build()).build();
		e.getChannel().write(message);	 
	}
}


This does work properly, but I want to make sure that I'm going about this
the recommended way.  If so, then probably this is a useful reminder to
others to handle unnoticed disconnection.

Thanks, Ian


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