An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.

本次为心跳---Fri Aug 11 13:49:08 CST 2023
2023-08-11 13:49:08.839  WARN 101880 --- [ntLoopGroup-3-1] io.netty.channel.DefaultChannelPipeline  : An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.

io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
	at io.netty.buffer.AbstractReferenceCountedByteBuf.release0(AbstractReferenceCountedByteBuf.java:110) ~[netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:98) ~[netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.buffer.DefaultByteBufHolder.release(DefaultByteBufHolder.java:117) ~[netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.util.ReferenceCountUtil.release(ReferenceCountUtil.java:84) ~[netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:112) [netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:373) [netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:359) [netty-all-4.1.6.Final.jar:4.1.6.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:351) [netty-all-4.1.6.Final.jar:4.1.6.Final]
	at com.hua.hello.netty.handler.HeartBeatHandler.channelRead0(HeartBeatHandler.java:40) [classes/:na]
	at com.hua.hello.netty.handler.HeartBeatHandler.channelRead0(HeartBeatHandler.java:11) [classes/:na]

问题发生原因是服务端末尾的(自定义的)handler没有处理好造成的。

解决办法：