[1.8.9] Error receiving packet from Spigot Server [solved?]

[JoelGodOfWar]

I can send a packet to my Spigot plugin, and can send one back to my Forge mod, but when the mod tries to decode the message i get an error. The client message to the server is simply 1234567890, the response from the plugin is AaBbCcDdEe. I feel like i'm missing something simple. I've searched google for days, and there are a lot of tutorials on sending packets, but none on receiving them. The plugin is receiving, and sending on channel "JSCM|INIT".

 

Error

[22:51:17] [Netty Client IO #1/ERROR] [FML]: FMLIndexedMessageCodec exception caught
io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Undefined message for discriminator 48 in channel JSCM|INIT
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:99) ~[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:90) [FMLProxyPacket.class:?]
at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:158) [NetworkManager.class:?]
at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:54) [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:389) [NetworkDispatcher.class:?]
at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:255) [NetworkDispatcher.class:?]
at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:53) [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.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:163) [byteToMessageDecoder.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.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:163) [byteToMessageDecoder.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.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:163) [byteToMessageDecoder.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.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.timeout.ReadTimeoutHandler.channelRead(ReadTimeoutHandler.java:150) [ReadTimeoutHandler.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.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:130) [AbstractNioByteChannel$NioByteUnsafe.class:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511) [NioEventLoop.class:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468) [NioEventLoop.class:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382) [NioEventLoop.class:4.0.23.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354) [NioEventLoop.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(Unknown Source) [?:1.7.0_79]

 

My code is below

import io.netty.buffer.ByteBuf;
import net.minecraft.client.Minecraft;
import net.minecraftforge.fml.common.network.ByteBufUtils;
import net.minecraftforge.fml.common.network.simpleimpl.IMessage;
import net.minecraftforge.fml.common.network.simpleimpl.IMessageHandler;
import net.minecraftforge.fml.common.network.simpleimpl.MessageContext;
import net.minecraftforge.fml.relauncher.Side;

public class MyMessage implements IMessage {
   
private String text;

    public MyMessage() { }

    public MyMessage(String text) {
        this.text = text;
    }

    @Override
    public void fromBytes(ByteBuf buf) {
        text = ByteBufUtils.readUTF8String(buf); // this class is very useful in general for writing more complex objects
    	
    }

    @Override
    public void toBytes(ByteBuf buf) {
        ByteBufUtils.writeUTF8String(buf, text);
    	
    }

    public static class Handler implements IMessageHandler<MyMessage, IMessage> {
        @Override
        public IMessage onMessage(final MyMessage message, final MessageContext ctx) {
            //IThreadListener mainThread = (WorldServer) ctx.getServerHandler().playerEntity.worldObj; // or Minecraft.getMinecraft() on the client
        	
        	if (ctx.side != Side.CLIENT) {
        	      System.err.println("TargetEffectMessageToClient received on wrong side:" + ctx.side);
        	      return null;
        	    }else{
        	    	System.out.println("MyMessage else triggered.................................................................");
        	    	Minecraft minecraft = Minecraft.getMinecraft();
        	minecraft.addScheduledTask(new Runnable() {
                @Override
                public void run() {
                	System.out.println("Run has been triggered.................................................................");
                	System.out.println(String.format("Received %s from %s", message.text, ctx.getServerHandler().playerEntity.getDisplayName()));
                }
            });
            return null; // no response in this case
        }}	
    }
}

 

PreInit

network = NetworkRegistry.INSTANCE.newSimpleChannel("JSCM|INIT");
    network.registerMessage(MyMessage.Handler.class, MyMessage.class, 0, Side.CLIENT);

 

[Ernio]

Forge packets start with discriminator (packet id). All packets sent from or received on spigot plugin must add that value on encoding/decoding.

Readup callbacks (when packet is sent).

[JoelGodOfWar]

Ok i messed up when trying to thank Ernio and diesieben07, and removed my previous post about the discriminator byte.

 

Anyways, i have got the code working by sending 50 characters to the Spigot plugin, then grabbing the discriminator, parse the message to send back to the client, then remove the length of the response from 50, adding extra 0's until the length is 50.

 

I then send the message to the client, with the discriminator, and the 50 character response, allowing me to remove the extra 0's, and then parse the message, for action by the mod.

 

After i clean up the code, i will post it here, for review, or help of others.

[Cool_Nick_Name]

I'm having the same problem. Can you explain what you did with more detail?