[SOLVED][1.19.2] Dev lost connection: Server sent an invalid packet, when world first loaded.

[gottsch]

I'm porting a mod from 1.18.2 to 1.19.2 and I'm forced exited on first world load (single-player) with this error:

Spoiler

...

[22:53:15] [Netty Server IO #1/ERROR] [minecraft/Connection]: Received class net.minecraft.network.protocol.game.ClientboundDisconnectPacket that couldn't be processed

java.lang.ClassCastException: class net.minecraft.server.network.ServerGamePacketListenerImpl cannot be cast to class net.minecraft.network.protocol.game.ClientGamePacketListener (net.minecraft.server.network.ServerGamePacketListenerImpl and net.minecraft.network.protocol.game.ClientGamePacketListener are in module [email protected] of loader 'TRANSFORMER' @ae73c80)

at net.minecraft.network.protocol.game.ClientboundDisconnectPacket.handle(ClientboundDisconnectPacket.java:7) ~[forge-1.19.2-43.2.0_mapped_official_1.19.2-recomp.jar%23183!/:?] {re:classloading}

at net.minecraft.network.Connection.genericsFtw(Connection.java:163) ~[forge-1.19.2-43.2.0_mapped_official_1.19.2-recomp.jar%23183!/:?] {re:classloading}

at net.minecraft.network.Connection.channelRead0(Connection.java:148) [forge-1.19.2-43.2.0_mapped_official_1.19.2-recomp.jar%23183!/:?] {re:classloading}

at net.minecraft.network.Connection.channelRead0(Connection.java:48) [forge-1.19.2-43.2.0_mapped_official_1.19.2-recomp.jar%23183!/:?] {re:classloading}

at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.local.LocalChannel.readInbound(LocalChannel.java:299) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.local.LocalChannel.finishPeerRead0(LocalChannel.java:445) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.local.LocalChannel.access$400(LocalChannel.java:50) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.channel.local.LocalChannel$5.run(LocalChannel.java:403) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174) [netty-common-4.1.77.Final.jar%23140!/:4.1.77.Final] {}

at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167) [netty-common-4.1.77.Final.jar%23140!/:4.1.77.Final] {}

at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470) [netty-common-4.1.77.Final.jar%23140!/:4.1.77.Final] {}

at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:503) [netty-transport-4.1.77.Final.jar%23137!/:4.1.77.Final] {}

at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:995) [netty-common-4.1.77.Final.jar%23140!/:4.1.77.Final] {}

at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [netty-common-4.1.77.Final.jar%23140!/:4.1.77.Final] {}

at java.lang.Thread.run(Thread.java:833) [?:?] {}

[22:53:15] [Server thread/INFO] [minecraft/ServerGamePacketListenerImpl]: Dev lost connection: Server sent an invalid packet

...

And then I'm prompted with the "Return to Server list" screen. I can then load the world (2nd attempt) without any problems.

Any help would be appreciated,

Thanks.

Edited January 17, 2023 by gottsch
solved

[warjort]

You need to post a link to the logs/debug.log so we can see if there is a previous error.

This kind of problem is caused by mods with broken networking code. It is normally difficult to find the problem mod.

Usually you have to experiment with removing mods until the problem goes away. (Backup your world before removing mods).

 

An FAQ in this forum used to be using the wrong version of journeymap for 1.19.2

But that problem seems to have disappeared now that journeymap has a final release for 1.19.2

[warjort]

I missed the part where it says you are porting a mod. 🙂 

If it is your mod causing the problem then you need to check there is no mismatch in the serialization of your network packets  e.g. deserailizing fields in the wrong order to how they are serailized or something else that will cause the networking to get "out-of-sync".

https://forge.gemwire.uk/wiki/SimpleChannel#Common_Packet_Handling_Pitfalls

 

Things like custom recipe serialization falls under this as well.

Edited January 17, 2023 by warjort

[gottsch]

Thanks for the quick reply.  It is my mod that is causing the issue (the only mod i'm testing). I've traced it down to handling the message received on the client. This line is failing:

Optional<Level> clientWorld = LogicalSidedProvider.CLIENTWORLD.get(sideReceived);

where sideReceived = LogicalSide.CLIENT

 

And i want to reiterate this only happens on the 1st attempt to load the world after launching Minecraft. Everything works fine when attempting to load the world again. 

[gottsch]

Solved.

I had to updated to

ctx.enqueueWork(() ->
// make sure it's only executed on the physical client
DistExecutor.unsafeRunWhenOn(Dist.CLIENT, () -> () -> processMessage(ctx, message))
);

instead of

ctx.enqueueWork(() -> processMessage(ctx, message));

(Not sure why though as this hasn't been a problem in prior versions of MC/Forge)