[MC-271325] Server attempts to send disconnect packets in the status phase

Clients invalidly handling their connection during the status phase will cause a SocketException to be thrown, which is handled by the ClientConnection#exceptionCaught method. This results in a clientbound/minecraft:disconnect packet with the message 'Internal Exception: (stringified error)'to be sent to the client. However, this packet doesn't exist in the status phase, so the server logs the following exception:

Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'

Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'

I would expect this exception to not be thrown as sending a disconnect packet with text during the status phase makes no sense, and the true error is with the client rather than the server.

Linked issues

is duplicated by 1

MC-273973 Error sending packet 'clientbound/minecraft:disconnect' repeatedly appears in server log Resolved

Attachments

latest.log

log-2024-05-01.txt

Comments 26

AdorableCat 2024-05-02T10:45:37Z

I attached log-2024-05-01.txt, it goes along with this packet capture file that was too large for me to upload: https://drive.google.com/file/d/1l1RAHCC_-rwh8S2B1PO3YecRxdpyFvO0/view?usp=sharing

The issue happens at the times

[21:55:41] packet 11267
[23:46:39] packet 14259
[00:11:10] packet 14940
[00:13:02] packet 14990
[02:41:30] packet 18900
[04:47:41] packet 22144
[05:33:36] packet 23300

Kiz 2024-05-15T21:48:28Z

Affects 24w20a.

Kiz 2024-05-22T17:42:35Z

Affects 24w21b.

Kiz 2024-06-02T16:20:13Z

Affects 1.21 Pre-release 2.

sh20000sh 2024-06-09T01:48:59Z

Seems like this is breach attempt from old exploit. When older version, you might observed log that says something like <known player> disconnected from <not matching IP address>.

Seems like this is some kind of side effect of patching that exploit (or just updating java version). I experienced server crash when server processing these kind of errors.

16 more comments

haykam 2024-07-08T05:22:35Z

There seems to be a Fabric mod which implements a fix for this bug: Disconnect Packet Fix

nraygun 2024-10-13T02:51:12Z

Can anyone provide an update on this bug?

ServerOyster 2024-12-14T15:42:48Z

Happens on 1.21.3, on all Bukkit forks and Vanilla. This has been freaking me out for ages!

[Mod] turbo 2024-12-14T17:03:54Z

@unknown: 1.21.3 is outdated and no longer supported on this bug tracker. Please only confirm issues for the latest version (1.21.4+).

MathiasMC 2024-12-16T19:22:17Z

Also happens on 1.21.4

[02:01:14] [Server thread/INFO]: Server empty for 60 seconds, pausing
[04:47:06] [Netty Epoll Server IO #20/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at ym.a(SourceFile:47) ~[server-1.21.4.jar:?]
        at ym.encode(SourceFile:14) ~[server-1.21.4.jar:?]
        at vu.a(SourceFile:26) ~[server-1.21.4.jar:?]
        at vu.encode(SourceFile:12) ~[server-1.21.4.jar:?]
        at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at vi$2.write(SourceFile:530) ~[server-1.21.4.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at vi.c(SourceFile:350) ~[server-1.21.4.jar:?]
        at vi.b(SourceFile:343) ~[server-1.21.4.jar:?]
        at vi.a(SourceFile:325) ~[server-1.21.4.jar:?]
        at vi.a(SourceFile:319) ~[server-1.21.4.jar:?]
        at vi.exceptionCaught(SourceFile:170) ~[server-1.21.4.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.handleReadException(AbstractEpollStreamChannel.java:727) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:825) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.115.Final.jar:4.1.115.Final]
        at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

[02:01:14] [Server thread/INFO]: Server empty for 60 seconds, pausing
[04:47:06] [Netty Epoll Server IO #20/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at ym.a(SourceFile:47) ~[server-1.21.4.jar:?]
        at ym.encode(SourceFile:14) ~[server-1.21.4.jar:?]
        at vu.a(SourceFile:26) ~[server-1.21.4.jar:?]
        at vu.encode(SourceFile:12) ~[server-1.21.4.jar:?]
        at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at vi$2.write(SourceFile:530) ~[server-1.21.4.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at vi.c(SourceFile:350) ~[server-1.21.4.jar:?]
        at vi.b(SourceFile:343) ~[server-1.21.4.jar:?]
        at vi.a(SourceFile:325) ~[server-1.21.4.jar:?]
        at vi.a(SourceFile:319) ~[server-1.21.4.jar:?]
        at vi.exceptionCaught(SourceFile:170) ~[server-1.21.4.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.handleReadException(AbstractEpollStreamChannel.java:727) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:825) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399) ~[netty-transport-classes-epoll-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.115.Final.jar:4.1.115.Final]
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.115.Final.jar:4.1.115.Final]
        at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

CER 2025-01-08T17:59:56Z

Also happens without any players currently being online, or recently disconnected:

[01:03:41] [Server thread/INFO]: USERNAME lost connection: Disconnected
[01:03:41] [Server thread/INFO]: USERNAME left the game

[01:03:41] [Server thread/INFO]: USERNAME lost connection: Disconnected
[01:03:41] [Server thread/INFO]: USERNAME left the game

Last player online left, then this error happens multiple times, here's one of them, no player activity since 01:03:41

[10:06:22] [Netty Server IO #28/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at knot/net.minecraft.class_9136.method_56426(class_9136.java:47) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_9136.encode(class_9136.java:14) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2545.method_10838(class_2545.java:26) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2545.encode(class_2545.java:12) ~[server-intermediary.jar:?]
        at knot/io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/net.minecraft.class_2535$2.write(class_2535.java:530) ~[server-intermediary.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/net.minecraft.class_2535.method_36942(class_2535.java:350) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_10764(class_2535.java:343) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.redirect$zzf000$antixray$redirectSendPacket(class_2535.java:796) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_52906(class_2535.java:325) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_10752(class_2535.java:319) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.exceptionCaught(class_2535.java:170) ~[server-intermediary.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.115.Final.jar:?]
        at knot/io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.115.Final.jar:?]
        at java.base/java.lang.Thread.run(Thread.java:1570) [?:?]

[10:06:22] [Netty Server IO #28/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at knot/net.minecraft.class_9136.method_56426(class_9136.java:47) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_9136.encode(class_9136.java:14) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2545.method_10838(class_2545.java:26) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2545.encode(class_2545.java:12) ~[server-intermediary.jar:?]
        at knot/io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/net.minecraft.class_2535$2.write(class_2535.java:530) ~[server-intermediary.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/net.minecraft.class_2535.method_36942(class_2535.java:350) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_10764(class_2535.java:343) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.redirect$zzf000$antixray$redirectSendPacket(class_2535.java:796) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_52906(class_2535.java:325) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_10752(class_2535.java:319) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.exceptionCaught(class_2535.java:170) ~[server-intermediary.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.115.Final.jar:?]
        at knot/io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.115.Final.jar:?]
        at java.base/java.lang.Thread.run(Thread.java:1570) [?:?]

Version: 1.21.4 (Fabric)

No thanks 2025-03-14T09:40:29Z

I can confirm it for 1.21.4.

Luke Russell 2025-04-02T21:10:09Z

Also happening for 1.21.5

[Netty Server IO #27/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
at zd.a(SourceFile:50) ~[server-1.21.5.jar:?]
at zd.encode(SourceFile:14) ~[server-1.21.5.jar:?]
at wj.a(SourceFile:26) ~[server-1.21.5.jar:?]
at wj.encode(SourceFile:12) ~[server-1.21.5.jar:?]
at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at vv$2.write(SourceFile:530) ~[server-1.21.5.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at vv.c(SourceFile:350) ~[server-1.21.5.jar:?]
at vv.b(SourceFile:343) ~[server-1.21.5.jar:?]
at vv.a(SourceFile:325) ~[server-1.21.5.jar:?]
at vv.a(SourceFile:319) ~[server-1.21.5.jar:?]
at vv.exceptionCaught(SourceFile:170) ~[server-1.21.5.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:796) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:732) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:658) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

virtualspan 2025-04-24T02:29:15Z

The only fix for this that I’ve found is this mod https://modrinth.com/mod/disconnect-packet-fix

Ammar 2025-05-28T18:17:03Z

Same here on 1.21.5 (fabric).

[16:56:39] [Server thread/INFO]: [REDACTED] left the game
[16:56:39] [Server thread/INFO]: Updating all forceload tickets for [REDACTED]
[16:57:39] [Server thread/INFO]: Server empty for 60 seconds, pausing
[17:16:18] [Netty Server IO #9/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
at knot/net.minecraft.class_9136.method_56426(class_9136.java:50) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_9136.encode(class_9136.java:14) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2545.method_10838(class_2545.java:26) [server-intermediary.jar:?]
at knot/net.minecraft.class_2545.encode(class_2545.java:12) [server-intermediary.jar:?]
at knot/io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) [netty-codec-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) [netty-transport-4.1.118.Final.jar:?]
at knot/net.minecraft.class_2535$2.write(class_2535.java:530) [server-intermediary.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) [netty-transport-4.1.118.Final.jar:?]
at knot/net.minecraft.class_2535.method_36942(class_2535.java:350) [server-intermediary.jar:?]
at knot/net.minecraft.class_2535.method_10764(class_2535.java:343) [server-intermediary.jar:?]
at knot/net.minecraft.class_2535.method_52906(class_2535.java:325) [server-intermediary.jar:?]
at knot/net.minecraft.class_2535.method_10752(class_2535.java:319) [server-intermediary.jar:?]
at knot/net.minecraft.class_2535.exceptionCaught(class_2535.java:170) [server-intermediary.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:796) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:732) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:658) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) [netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) [netty-common-4.1.118.Final.jar:?]
at knot/io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [netty-common-4.1.118.Final.jar:?]
at java.base/java.lang.Thread.run(Thread.java:1447) [?:?]

Stoupy 2025-06-01T13:46:48Z

I’m having the same log errors in 1.21.6 PreRelease-1

[15:42:01] [Netty Server IO #15/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at zl.a(SourceFile:50) ~[server-1.21.6-pre1.jar:?]
        at zl.encode(SourceFile:14) ~[server-1.21.6-pre1.jar:?]
        at wr.a(SourceFile:26) ~[server-1.21.6-pre1.jar:?]
        at wr.encode(SourceFile:12) ~[server-1.21.6-pre1.jar:?]
        at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at wd$2.write(SourceFile:525) ~[server-1.21.6-pre1.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at wd.c(SourceFile:351) ~[server-1.21.6-pre1.jar:?]
        at wd.b(SourceFile:343) ~[server-1.21.6-pre1.jar:?]
        at wd.a(SourceFile:325) ~[server-1.21.6-pre1.jar:?]
        at wd.a(SourceFile:319) ~[server-1.21.6-pre1.jar:?]
        at wd.exceptionCaught(SourceFile:170) ~[server-1.21.6-pre1.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:796) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:732) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:658) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
        at java.base/java.lang.Thread.run(Thread.java:1570) [?:?]

[15:42:01] [Netty Server IO #15/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at zl.a(SourceFile:50) ~[server-1.21.6-pre1.jar:?]
        at zl.encode(SourceFile:14) ~[server-1.21.6-pre1.jar:?]
        at wr.a(SourceFile:26) ~[server-1.21.6-pre1.jar:?]
        at wr.encode(SourceFile:12) ~[server-1.21.6-pre1.jar:?]
        at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at wd$2.write(SourceFile:525) ~[server-1.21.6-pre1.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at wd.c(SourceFile:351) ~[server-1.21.6-pre1.jar:?]
        at wd.b(SourceFile:343) ~[server-1.21.6-pre1.jar:?]
        at wd.a(SourceFile:325) ~[server-1.21.6-pre1.jar:?]
        at wd.a(SourceFile:319) ~[server-1.21.6-pre1.jar:?]
        at wd.exceptionCaught(SourceFile:170) ~[server-1.21.6-pre1.jar:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:796) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:732) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:658) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
        at java.base/java.lang.Thread.run(Thread.java:1570) [?:?]

Luke Bilston 2025-06-05T08:32:52Z

1.21.6 Pre release 2 having this happen as well, server was empty and paused right before line 1 below.

[01:40:02] [Netty Epoll Server IO #14/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
	at zl.a(SourceFile:50) ~[server-1.21.6-pre2.jar:?]
	at zl.encode(SourceFile:14) ~[server-1.21.6-pre2.jar:?]
	at wr.a(SourceFile:26) ~[server-1.21.6-pre2.jar:?]
	at wr.encode(SourceFile:12) ~[server-1.21.6-pre2.jar:?]
	at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd$2.write(SourceFile:525) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd.c(SourceFile:351) ~[server-1.21.6-pre2.jar:?]
	at wd.b(SourceFile:343) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:325) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:319) ~[server-1.21.6-pre2.jar:?]
	at wd.exceptionCaught(SourceFile:170) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.handleReadException(AbstractEpollStreamChannel.java:727) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:825) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]
[08:13:28] [Netty Epoll Server IO #18/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
	at zl.a(SourceFile:50) ~[server-1.21.6-pre2.jar:?]
	at zl.encode(SourceFile:14) ~[server-1.21.6-pre2.jar:?]
	at wr.a(SourceFile:26) ~[server-1.21.6-pre2.jar:?]
	at wr.encode(SourceFile:12) ~[server-1.21.6-pre2.jar:?]
	at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd$2.write(SourceFile:525) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd.c(SourceFile:351) ~[server-1.21.6-pre2.jar:?]
	at wd.b(SourceFile:343) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:325) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:319) ~[server-1.21.6-pre2.jar:?]
	at wd.exceptionCaught(SourceFile:170) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.handleReadException(AbstractEpollStreamChannel.java:727) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:825) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

[01:40:02] [Netty Epoll Server IO #14/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
	at zl.a(SourceFile:50) ~[server-1.21.6-pre2.jar:?]
	at zl.encode(SourceFile:14) ~[server-1.21.6-pre2.jar:?]
	at wr.a(SourceFile:26) ~[server-1.21.6-pre2.jar:?]
	at wr.encode(SourceFile:12) ~[server-1.21.6-pre2.jar:?]
	at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd$2.write(SourceFile:525) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd.c(SourceFile:351) ~[server-1.21.6-pre2.jar:?]
	at wd.b(SourceFile:343) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:325) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:319) ~[server-1.21.6-pre2.jar:?]
	at wd.exceptionCaught(SourceFile:170) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.handleReadException(AbstractEpollStreamChannel.java:727) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:825) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]
[08:13:28] [Netty Epoll Server IO #18/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
	at zl.a(SourceFile:50) ~[server-1.21.6-pre2.jar:?]
	at zl.encode(SourceFile:14) ~[server-1.21.6-pre2.jar:?]
	at wr.a(SourceFile:26) ~[server-1.21.6-pre2.jar:?]
	at wr.encode(SourceFile:12) ~[server-1.21.6-pre2.jar:?]
	at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd$2.write(SourceFile:525) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at wd.c(SourceFile:351) ~[server-1.21.6-pre2.jar:?]
	at wd.b(SourceFile:343) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:325) ~[server-1.21.6-pre2.jar:?]
	at wd.a(SourceFile:319) ~[server-1.21.6-pre2.jar:?]
	at wd.exceptionCaught(SourceFile:170) ~[server-1.21.6-pre2.jar:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.handleReadException(AbstractEpollStreamChannel.java:727) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:825) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399) ~[netty-transport-classes-epoll-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:4.1.118.Final]
	at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

Sock 2025-06-22T17:57:11Z

Happening on Fabric 1.21.6 for me too.
[11:04:34] [Server thread/INFO]: [USERNAME] left the game
[11:05:34] [Server thread/INFO]: Server empty for 60 seconds, pausing
[12:19:30] [Netty Server IO #11/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
at knot/net.minecraft.class_9136.method_56426(class_9136.java:50) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_9136.encode(class_9136.java:14) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2545.method_10838(class_2545.java:26) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2545.encode(class_2545.java:12) ~[server-intermediary.jar:?]
at knot/io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.118.Final.jar:?]
at knot/net.minecraft.class_2535$2.write(class_2535.java:525) ~[server-intermediary.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.118.Final.jar:?]
at knot/net.minecraft.class_2535.method_36942(class_2535.java:351) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2535.method_10764(class_2535.java:343) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2535.method_52906(class_2535.java:325) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2535.method_10752(class_2535.java:319) ~[server-intermediary.jar:?]
at knot/net.minecraft.class_2535.exceptionCaught(class_2535.java:170) ~[server-intermediary.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:796) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:732) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:658) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.118.Final.jar:?]
at knot/io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998) ~[netty-common-4.1.118.Final.jar:?]
at knot/io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.118.Final.jar:?]
at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

Braiden Boss 2025-07-13T18:10:36Z

I have this same bug on my 1.21.6 server. hopefully it gets fixed.

Mataeo 2025-07-15T16:25:45Z

I also have this happening, also 1.21.6 server. Anyone have any idea why it is happening or how to fix?

chrstffr 2025-07-25T19:44:02Z

Can confirm. Still happening in 1.21.8.

Pascal Roy 2025-09-12T19:42:08Z

It’s been happening for over a year. It’s completely polluting the log files to the point of rendering them almost useless, composing over 95% of the content for a low activity server like a home one.

sh20000sh 2025-12-10T00:45:51Z

Can’t it just be some compact log for those kind of exception?

sh20000sh 2025-12-10T01:36:29Z

Log itself doesn’t show any remote ip address, but when you see active TCP connections, there are some connection. Blocking ip related with that connection with firewall can be temporary fix.

sh20000sh 2025-12-10T02:07:51Z

I think server should automatically add those ip to blacklist when it got those exception. Looks like there’s bot trying old exploit that existed before 1.20.6

sh20000sh 2025-12-19T02:52:51Z

I’m now logging all established TCP connection to port 25565. There are some connection that MC Server doesn’t display. Some of them make server throw exception like an hour after that.