Communication between Forge mod and Bukkit plugin

[TheASTRO]

Hello AGAIN! (I know that Bukkit is dead  ) So I am trying to create a mod and a plugin that could communicate with each other. By the way, I need to send a simple message to Forge mod from the plugin. I found the old thread, which was written for 1.7.10 by one of the forums staff member and a guy :). Here is the code from old 2015:

//Forge part:
// --- Main class ---
@Mod.EventHandler
public void preInit(FMLPreInitializationEvent event)
{
    SimpleNetworkWrapper network = NetworkRegistry.INSTANCE.newSimpleChannel("Channel");
    network.registerMessage(CommunicationMessage.Handler.class, CommunicationMessage.class, 0, Side.CLIENT);
    System.out.println("Channel registered as CLIENT Side with 0");
}

//--- CommunicationMessage class ---
  public class CommunicationMessage implements IMessage {

    private String text;

    public CommunicationMessage() {
    }

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

    @Override
    public void fromBytes(ByteBuf buf) {
        text = ByteBufUtils.readUTF8String(buf);
    }

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

    public static class Handler implements IMessageHandler<CommunicationMessage, IMessage> {

        @Override
        public IMessage onMessage(CommunicationMessage message, MessageContext ctx) {
            System.out.println(String.format("Received %s from %s", message.text, ctx.getServerHandler().playerEntity.getDisplayName()));
            return null; // no response in this case
        }
    }
}

//Bukkit part:
//--- Main plugin class (In onEnable()): ---

Bukkit.getMessenger().registerOutgoingPluginChannel(this, "Channel");

 

I really want to create this mod-plugin connection. I have great ideas, but I need some base. PLEASE, help me with this. Thanks in advance!!!

[TheASTRO]

2 minutes ago, diesieben07 said:

You already have most of what you need. You just have to write the code in bukkit to read/write the same data (and the message ID) to the stream like you do in FML

So Forge code is okay? Wow... May I ask you to write a piece of code for Bukkit part? Cause I don`t really get into how to do that...

[TheASTRO]

1 minute ago, diesieben07 said:

I have never worked with Bukkit. You have to look at the Bukkit documentation on how to send and receive custom payload messages

Okey, I will do my best. The last test - is Forge code alright?  Thanks

[TheASTRO]

Ok, Thanks!

[TheASTRO]

2 hours ago, diesieben07 said:

Mostly. Please read the docs on networking if you are unsure.

Done some work. Here is a plugin:

Plugin plugin = this;
	
	@EventHandler(priority = EventPriority.NORMAL)
	public void onPlayerPickupItem(PlayerPickupItemEvent event) {
		Player player = event.getPlayer();
		System.out.println("Sent message");
		player.sendPluginMessage(plugin, "Channel", "u there".getBytes());
		//player.sendPluginMessage(plugin, "Channel", new byte[]{});
		System.out.println("Maybe complete...");
	}

When I pickup an item, server throws fatal error and terminates connection 

Minecraft output:

Spoiler

[17:16:53] [Client thread/ERROR] [FML]: FMLIndexedMessageCodec exception caught
io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Undefined message for discriminator 117 in channel Channel
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:99) ~[MessageToMessageDecoder.class:?]
    at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:?]
    at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
    at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) [DefaultChannelPipeline.class:?]
    at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) [EmbeddedChannel.class:?]
    at cpw.mods.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:86) [FMLProxyPacket.class:?]
    at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:241) [NetworkManager.class:?]
    at net.minecraft.client.multiplayer.PlayerControllerMP.updateController(PlayerControllerMP.java:317) [PlayerControllerMP.class:?]
    at net.minecraft.client.Minecraft.runTick(Minecraft.java:1693) [Minecraft.class:?]
    at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1039) [Minecraft.class:?]
    at net.minecraft.client.Minecraft.run(Minecraft.java:962) [Minecraft.class:?]
    at net.minecraft.client.main.Main.main(Main.java:164) [Main.class:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_121]
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
    at net.minecraftforge.gradle.GradleStartCommon.launch(Unknown Source) [start/:?]
    at GradleStart.main(Unknown Source) [start/:?]
Caused by: java.lang.NullPointerException: Undefined message for discriminator 117 in channel Channel
    at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:73) ~[FMLIndexedMessageToMessageCodec.class:?]
    at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:17) ~[FMLIndexedMessageToMessageCodec.class:?]
    at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81) ~[MessageToMessageCodec$2.class:?]
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:89) ~[MessageToMessageDecoder.class:?]
    ... 20 more
[17:16:53] [Client thread/ERROR] [FML]: SimpleChannelHandlerWrapper exception
io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Undefined message for discriminator 117 in channel Channel
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:99) ~[MessageToMessageDecoder.class:?]
    at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:?]
    at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
    at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) [DefaultChannelPipeline.class:?]
    at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) [EmbeddedChannel.class:?]
    at cpw.mods.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:86) [FMLProxyPacket.class:?]
    at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:241) [NetworkManager.class:?]
    at net.minecraft.client.multiplayer.PlayerControllerMP.updateController(PlayerControllerMP.java:317) [PlayerControllerMP.class:?]
    at net.minecraft.client.Minecraft.runTick(Minecraft.java:1693) [Minecraft.class:?]
    at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1039) [Minecraft.class:?]
    at net.minecraft.client.Minecraft.run(Minecraft.java:962) [Minecraft.class:?]
    at net.minecraft.client.main.Main.main(Main.java:164) [Main.class:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_121]
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
    at net.minecraftforge.gradle.GradleStartCommon.launch(Unknown Source) [start/:?]
    at GradleStart.main(Unknown Source) [start/:?]
Caused by: java.lang.NullPointerException: Undefined message for discriminator 117 in channel Channel
    at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:73) ~[FMLIndexedMessageToMessageCodec.class:?]
    at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:17) ~[FMLIndexedMessageToMessageCodec.class:?]
    at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81) ~[MessageToMessageCodec$2.class:?]
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:89) ~[MessageToMessageDecoder.class:?]
    ... 20 more
[17:16:53] [Client thread/ERROR] [FML]: There was a critical exception handling a packet on channel Channel
io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Undefined message for discriminator 117 in channel Channel
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:99) ~[MessageToMessageDecoder.class:?]
    at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:?]
    at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) ~[DefaultChannelHandlerContext.class:?]
    at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) ~[DefaultChannelHandlerContext.class:?]
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) ~[DefaultChannelPipeline.class:?]
    at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) ~[EmbeddedChannel.class:?]
    at cpw.mods.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:86) [FMLProxyPacket.class:?]
    at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:241) [NetworkManager.class:?]
    at net.minecraft.client.multiplayer.PlayerControllerMP.updateController(PlayerControllerMP.java:317) [PlayerControllerMP.class:?]
    at net.minecraft.client.Minecraft.runTick(Minecraft.java:1693) [Minecraft.class:?]
    at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1039) [Minecraft.class:?]
    at net.minecraft.client.Minecraft.run(Minecraft.java:962) [Minecraft.class:?]
    at net.minecraft.client.main.Main.main(Main.java:164) [Main.class:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_121]
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
    at net.minecraftforge.gradle.GradleStartCommon.launch(Unknown Source) [start/:?]
    at GradleStart.main(Unknown Source) [start/:?]
Caused by: java.lang.NullPointerException: Undefined message for discriminator 117 in channel Channel
    at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:73) ~[FMLIndexedMessageToMessageCodec.class:?]
    at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:17) ~[FMLIndexedMessageToMessageCodec.class:?]
    at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81) ~[MessageToMessageCodec$2.class:?]
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:89) ~[MessageToMessageDecoder.class:?]
    ... 20 more

 

Maaaaybe someone will see this post and help me. Thats it

[TheASTRO]

1 hour ago, diesieben07 said:

Like I said before, you need to first send the packet ID as a byte before sending the actual message contents. Moreover, getBytes and read/writeUTF8String are not compatible. getBytes does not produce UTF-8, you need to pass in the UTF-8 Charset.

Searched the Internet, even asked a question on StuckOverFlow, and everyone suggest using getBytes. I have no idea to convert string to UTF-8 and then place to byte array..

[TheASTRO]

13 minutes ago, diesieben07 said:

getBytes is fine, but you need to pass the charset. getBytes without arguments uses the platform default charset, which is almost never what you want. Pass in StandardCharsets.UTF_8 and you will always get utf-8.

I am literally crying... Really. I made so many attempts... Made it:

String s = "some text here";
byte[] b = s.getBytes(StandardCharsets.UTF_8);

And the error is the same:

io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Undefined message for discriminator 115 in channel Channel

Decoder.. I thought it is about Charset. But now it is UTF-8 and it still doesn`t work. 

[TheASTRO]

4 minutes ago, diesieben07 said:

 

If you still have a little patience, then explain it how to make that... Thanks for your patience and support!

[TheASTRO]

5 minutes ago, diesieben07 said:

The easiest way is to construct your byte array is using ByteArrayDataOutput, which is a DataOutput extension which doesn't throw checked exceptions and produces a byte array.

And it has to be on Bukkit or Forge side?

[Franckyi]

I think on the Bukkit side, because Forge already knows which discriminator to use, whereas Bukkit doesn't.

[TheASTRO]

Sooo many information. Thanks for tour help A LOT!