Syncing Capabilities through packets returns Casting exception.

[oldcheese]

Hey again. I've managed to succesfully implement a few different capabilities. However when I open a world the Server gets the correct values while my client doesn't. To solve this I thought I'd implement a packet that sends NBT data to the client and uses my Capabilities wrapper to set the correct values.

 

The error I get is the following: 

java.lang.ClassCastException: net.minecraft.client.network.NetHandlerPlayClient cannot be cast to net.minecraft.network.NetHandlerPlayServer
	at net.minecraftforge.fml.common.network.simpleimpl.MessageContext.getServerHandler(MessageContext.java:55) ~[MessageContext.class:?]
	at com.cheese.rpvp.capabilities.synchers.BarMessage$MessageHandler.onMessage(BarMessage.java:46) ~[BarMessage$MessageHandler.class:?]
	at com.cheese.rpvp.capabilities.synchers.BarMessage$MessageHandler.onMessage(BarMessage.java:38) ~[BarMessage$MessageHandler.class:?]
	at net.minecraftforge.fml.common.network.simpleimpl.SimpleChannelHandlerWrapper.channelRead0(SimpleChannelHandlerWrapper.java:56) ~[SimpleChannelHandlerWrapper.class:?]
	at net.minecraftforge.fml.common.network.simpleimpl.SimpleChannelHandlerWrapper.channelRead0(SimpleChannelHandlerWrapper.java:36) ~[SimpleChannelHandlerWrapper.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) ~[SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103) ~[MessageToMessageDecoder.class:4.0.23.Final]
	at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) ~[DefaultChannelPipeline.class:4.0.23.Final]
	at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) ~[EmbeddedChannel.class:4.0.23.Final]
	at net.minecraftforge.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:109) [FMLProxyPacket.class:?]
	at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:157) [NetworkManager.class:?]
	at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:51) [NetworkManager.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.handleClientSideCustomPacket(NetworkDispatcher.java:410) [NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:276) [NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:73) [NetworkDispatcher.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) [DefaultChannelPipeline.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel.finishPeerRead(LocalChannel.java:326) [LocalChannel.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel.access$400(LocalChannel.java:45) [LocalChannel.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel$5.run(LocalChannel.java:312) [LocalChannel$5.class:4.0.23.Final]
	at io.netty.channel.local.LocalEventLoop.run(LocalEventLoop.java:33) [LocalEventLoop.class:4.0.23.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [SingleThreadEventExecutor$2.class:4.0.23.Final]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_144]

 

My classes are as follows: 

package com.cheese.rpvp.capabilities.synchers;

import net.minecraftforge.fml.common.network.NetworkRegistry;
import net.minecraftforge.fml.common.network.simpleimpl.SimpleNetworkWrapper;

public class BarPacketHandler {

    public static final SimpleNetworkWrapper barWrapper = NetworkRegistry.INSTANCE.newSimpleChannel("rpvp");

}

This package defines my simpleChannel named rpvp after my client info. I create an instance of this class in my Main class with 

   public static BarPacketHandler packetHandler;

and then register it in my commonProxy like so:

BarPacketHandler.barWrapper.registerMessage(BarMessage.MessageHandler.class, BarMessage.class, 1, Side.CLIENT);

 

My goal here is to send a packet from the server (Since the server has the correct values) and pass them on to the client. Since the client needs to be updated. 

 

I subscribed an Event for PlayerLoggedInEvent that will get my Capability and save all relevant info to be updated to an NBTTagCompound and then calls the sendTo method from my Message class. 

    @SubscribeEvent
    public void loggedIn(PlayerLoggedInEvent event){
        if(!event.player.worldObj.isRemote) {
            if (event.player.hasCapability(CAPABILITY_BAR, EnumFacing.DOWN)) {
                final IBarHandler instance = getHandler(event.player);
                final NBTTagCompound tag = new NBTTagCompound();
                tag.setInteger("mana", instance.getMana());
                tag.setInteger("health", instance.getHealth());
                tag.setInteger("fatigue", instance.getFatigue());
                tag.setInteger("maxhealth", instance.getMaxHealth());
                tag.setInteger("maxmana", instance.getMaxMana());
                Main.packetHandler.barWrapper.sendTo(new BarMessage(tag), (EntityPlayerMP)event.player);
                System.out.println("Message sent");
            }
        }
    }

 

Then finally we have the actual BarMessage class with an inner class "MessageHandler". Both have the default method, so that can't be the error. 

 

public class BarMessage implements IMessage {
    public BarMessage(){}
    private NBTTagCompound toSend;
    public BarMessage(NBTTagCompound tag){
        this.toSend = tag;
    }

    @Override
    public void toBytes(ByteBuf buf) {
        System.out.println("toBytes called");
        ByteBufUtils.writeTag(buf, this.toSend);
    }

    @Override
    public void fromBytes(ByteBuf buf) {
        System.out.println("frombytes called");
        this.toSend = ByteBufUtils.readTag(buf);
    }
    public NBTTagCompound getTag(){
        return toSend;
    }

    public static class MessageHandler implements IMessageHandler<BarMessage, IMessage> {

        public MessageHandler(){}

        @Override
        public IMessage onMessage(BarMessage content, MessageContext ctx) {
            System.out.println("messagehandler called");

            EntityPlayerMP serverPlayer = ctx.getServerHandler().playerEntity;
            final IBarHandler handler = getHandler(serverPlayer);
            NBTTagCompound tag = content.toSend;
            handler.setMana(tag.getInteger("mana"));
            handler.setMaxMana(tag.getInteger("maxmana"));
            handler.setHealth(tag.getInteger("health"));
            handler.setMaxHealth(tag.getInteger("maxhealth"));
            handler.setFatigue(tag.getInteger("fatigue"));

            return null;
        }
    }
}

 

I have also tried a Variant of the onMessage where I've set content and ctx to final and tried to make an inner class that uses a scheduled task to set these things, but I assumed that since I'm not influencing the world directly it shouldn't be a problem. 

 

Now the main Issue 

I examined the MessageContext class, which returns the nethandler. Somewhere in my code I've somehow set my nethandler to NetHandlerPlayClient, and when I try to cast it using the getServerHandler it crashes since I only have the NetHandlerPlayClient.

 

I know I must be making some simple mistake that I overlooked, I've googled for a few hours now and It's driving me crazy.

 

I've tried to find a way to access playerEntity outside of the ctx, but that didn't work. I need playerEntity to pass to my getHandler(playerEntity) so I can call the methods for setting my Capabilities, the server sends the Target player with the message. so the Packet gets executed on the Client. I assumed that since I was running the handler on the client I could somehow use

 final IBarHandler handler = Minecraft.getMinecraft().thePlayer().GetCapability(CAPABILITY_BAR);

But that returned a nullpointer exception.

 

I've followed the documentation at https://mcforge.readthedocs.io/en/latest/networking/simpleimpl/ to the T, I don't quite understand what I'm doing wrong here, or what I could do to improve. Some hints would be appreciated.

[Animefan8888]

Please post the Null Pointer Exception and how you register your Capability.

Edited August 19, 2017 by Animefan8888

[oldcheese]

The Nullpointer exception only occurs when I try to register an entity from Minecraft.GetMinecraft.theplayer.getCapability instead of 

PlayerEntityMP player = ctx.getServer etc. etc.

 

java.lang.NullPointerException
	at com.cheese.rpvp.capabilities.synchers.BarMessage$MessageHandler.onMessage(BarMessage.java:47) ~[BarMessage$MessageHandler.class:?]
	at com.cheese.rpvp.capabilities.synchers.BarMessage$MessageHandler.onMessage(BarMessage.java:40) ~[BarMessage$MessageHandler.class:?]
	at net.minecraftforge.fml.common.network.simpleimpl.SimpleChannelHandlerWrapper.channelRead0(SimpleChannelHandlerWrapper.java:56) ~[SimpleChannelHandlerWrapper.class:?]
	at net.minecraftforge.fml.common.network.simpleimpl.SimpleChannelHandlerWrapper.channelRead0(SimpleChannelHandlerWrapper.java:36) ~[SimpleChannelHandlerWrapper.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) ~[SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103) ~[MessageToMessageDecoder.class:4.0.23.Final]
	at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) ~[AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) ~[DefaultChannelPipeline.class:4.0.23.Final]
	at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) ~[EmbeddedChannel.class:4.0.23.Final]
	at net.minecraftforge.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:109) [FMLProxyPacket.class:?]
	at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:157) [NetworkManager.class:?]
	at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:51) [NetworkManager.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.handleClientSideCustomPacket(NetworkDispatcher.java:410) [NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:276) [NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:73) [NetworkDispatcher.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) [DefaultChannelPipeline.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel.finishPeerRead(LocalChannel.java:326) [LocalChannel.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel.access$400(LocalChannel.java:45) [LocalChannel.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel$5.run(LocalChannel.java:312) [LocalChannel$5.class:4.0.23.Final]
	at io.netty.channel.local.LocalEventLoop.run(LocalEventLoop.java:33) [LocalEventLoop.class:4.0.23.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [SingleThreadEventExecutor$2.class:4.0.23.Final]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_144]

 

My Capability is registered in my main class in the preInit as such:

        CustomDataHandlerBar.register();

which obviously tells you nothing. the Barhandler is 

public class CustomDataHandlerBar {

    @CapabilityInject(IBarHandler.class)
    public static final Capability<IBarHandler> CAPABILITY_BAR = null;

    public static void register(){
        CapabilityManager.INSTANCE.register(IBarHandler.class, new Storage(), DefaultBarHandler.class);
        MinecraftForge.EVENT_BUS.register(new CustomDataHandlerBar());
    }

    @SubscribeEvent
    public void attachCapabilities(AttachCapabilitiesEvent<Entity> event){
        if(event.getObject() instanceof EntityPlayer)
            event.addCapability(new ResourceLocation(Main.MODID, "BARS"), new BarProvider());


    }
    @SubscribeEvent
    public void clonePlayer(PlayerEvent.Clone event){

        final IBarHandler original = getHandler(event.getOriginal());
        final IBarHandler clone = getHandler(event.getEntity());
        clone.setMana(original.getMana());
        clone.setMaxMana(original.getMaxMana());
        clone.setHealth(original.getHealth());
        clone.setMaxHealth(original.getMaxHealth());
        clone.setFatigue(original.getFatigue());
    }

    @SubscribeEvent
    public void loggedIn(PlayerLoggedInEvent event){
        if(!event.player.worldObj.isRemote) {
            if (event.player.hasCapability(CAPABILITY_BAR, EnumFacing.DOWN)) {
                final IBarHandler instance = getHandler(event.player);
                final NBTTagCompound tag = new NBTTagCompound();
                tag.setInteger("mana", instance.getMana());
                tag.setInteger("health", instance.getHealth());
                tag.setInteger("fatigue", instance.getFatigue());
                tag.setInteger("maxhealth", instance.getMaxHealth());
                tag.setInteger("maxmana", instance.getMaxMana());
                Main.packetHandler.barWrapper.sendTo(new BarMessage(tag), (EntityPlayerMP)event.player);
                System.out.println("Message sent");
            }
        }
    }

    public static IBarHandler getHandler(Entity entity){
            if(entity.hasCapability(CAPABILITY_BAR, EnumFacing.DOWN)){
                System.out.println("Player has capability");
                return entity.getCapability(CAPABILITY_BAR, EnumFacing.DOWN);
            }
        return null;
    }


}

 

I'm able to interact with the Capability and I'm able to set different values using items and equipment and such. I'm not sure if the problem lies with the Capability system.  Though I'm not entirely sure why the server end saves my information properly yet the Client doesn't synchronise with it.  The Forge classes are pretty complex for someone with only a year of Java experience and there's not a lot of online knowledge to find on the current version and what to use, I'm mostly just going by feel and the official docs, which also don't cover much.

 

That's why I'm creating the packet, to keep the client synchronized and to learn how to create packets for the future.

 

Also, when I comment out the Capabilities stuff in the original entityplayerMP = method I'm still getting the same Can't cast error. 

Edited August 19, 2017 by oldcheese
clarification.

[Draco18s]

 

Quote

 

Warning

As of Minecraft 1.8 packets are by default handled on the network thread.

That means that your IMessageHandler can not interact with most game objects directly. Minecraft provides a convenient way to make your code execute on the main thread instead using IThreadListener.addScheduledTask.

The way to obtain an IThreadListener is using either the Minecraft instance (client side) or a WorldServer instance (server side). The code above shows an example of this by getting a WorldServer instance from an EntityPlayerMP.

 

http://mcforge.readthedocs.io/en/latest/networking/simpleimpl/

Edited August 19, 2017 by Draco18s

[oldcheese]

2 minutes ago, Draco18s said:

 

http://mcforge.readthedocs.io/en/latest/networking/simpleimpl/

 

Welp. That's it. 

 

I've tried to change it to a similar code. But I was using ctx instead of Minecraft.GetMinecraft to initiate my IthreadListener.

 

It seems like every time I get stuck on something for multiple hours it turns out to be a big oversight I should've noticed.

 

 

For future readers who run into my topic. The final code for my onMessage ended up being 

 

        @Override
        public IMessage onMessage(final BarMessage content,final MessageContext ctx) {

            IThreadListener myThread = Minecraft.getMinecraft();
            myThread.addScheduledTask(new Runnable(){
                @Override
                public void run(){
                    System.out.println("messagehandler called");
                    final IBarHandler handler = Minecraft.getMinecraft().thePlayer.getCapability(CAPABILITY_BAR, EnumFacing.DOWN);
                    NBTTagCompound tag = content.toSend;
                    handler.setMana(tag.getInteger("mana"));
                    handler.setMaxMana(tag.getInteger("maxmana"));
                    handler.setHealth(tag.getInteger("health"));
                    handler.setMaxHealth(tag.getInteger("maxhealth"));
                    handler.setFatigue(tag.getInteger("fatigue"));

                }
            });
                return null;
        }

 

 

Thanks for the help everyone.