Ability to send data when player first enters the level

src/main/java/ru/bclib/api/dataexchange/DataExchangeAPI.java

@@ -3,8 +3,10 @@ package ru.bclib.api.dataexchange;
 import com.google.common.collect.Lists;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
+import net.fabricmc.fabric.api.client.networking.v1.ClientLoginConnectionEvents;
 import net.fabricmc.fabric.api.client.networking.v1.ClientPlayConnectionEvents;
 import net.fabricmc.fabric.api.networking.v1.ServerPlayConnectionEvents;
+import net.minecraft.client.Minecraft;
 import net.minecraft.network.FriendlyByteBuf;
 
 import java.util.HashSet;
@@ -34,7 +36,12 @@ public class DataExchangeAPI {
 	private void initClientside(){
 		if (client!=null) return;
 		client = new ConnectorClientside(this);
-		
+		ClientLoginConnectionEvents.INIT.register((a, b) ->{
+			System.out.println("INIT");
+		});
+		ClientLoginConnectionEvents.QUERY_START.register((a, b) ->{
+			System.out.println("INIT");
+		});
 		ClientPlayConnectionEvents.INIT.register(client::onPlayInit);
 		ClientPlayConnectionEvents.JOIN.register(client::onPlayReady);
 		ClientPlayConnectionEvents.DISCONNECT.register(client::onPlayDisconnect);
@@ -117,5 +124,21 @@ public class DataExchangeAPI {
 		}
 	}
 	
-	
+	/**
+	 * Automatically called before the player enters the world.
+	 * <p>
+	 * This will send all {@link DataHandler}-Objects that have {@link DataHandlerDescriptor#sendBeforeEnter} set to*
+	 * {@Code true},
+	 */
+	@Environment(EnvType.CLIENT)
+	public static void sendOnEnter(){
+		getInstance().descriptors.forEach((desc)-> {
+			if (desc.sendBeforeEnter){
+				DataHandler h = desc.JOIN_INSTANCE.get();
+				if (!h.getOriginatesOnServer()) {
+					getInstance().client.sendToServer(h);
+				}
+			}
+		});
+	}
 }

src/main/java/ru/bclib/api/dataexchange/DataHandler.java

@@ -1,7 +1,5 @@
 package ru.bclib.api.dataexchange;
 
-import io.netty.buffer.ByteBufUtil;
-import io.netty.util.CharsetUtil;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
@@ -44,7 +42,9 @@ public abstract class DataHandler {
 		client.execute(() -> runOnGameThread(client, null, true));
 	}
 	
+	private ServerPlayer lastMessageSender;
 	void receiveFromClient(MinecraftServer server, ServerPlayer player, ServerGamePacketListenerImpl handler, FriendlyByteBuf buf, PacketSender responseSender){
+		lastMessageSender = player;
 		deserializeFromIncomingData(buf, responseSender, false);
 		server.execute(() -> runOnGameThread(null, server, false));
 	}
@@ -53,11 +53,15 @@ public abstract class DataHandler {
 	}
 	
 	protected void runOnGameThread(Minecraft client, MinecraftServer server, boolean isClient){
-	
 	}
 	
 	protected void serializeData(FriendlyByteBuf buf) {
+	}
 	
+	final protected boolean reply(DataHandler message, MinecraftServer server){
+		if (lastMessageSender==null) return false;
+		message.sendToClient(server, lastMessageSender);
+		return true;
 	}
 	
 	void sendToClient(MinecraftServer server){

src/main/java/ru/bclib/api/dataexchange/DataHandlerDescriptor.java

@@ -6,21 +6,23 @@ import java.util.function.Supplier;
 
 public class DataHandlerDescriptor {
 	public DataHandlerDescriptor(ResourceLocation identifier, Supplier<DataHandler> instancer){
-		this(identifier, instancer, instancer, false);
+		this(identifier, instancer, instancer, false, false);
 	}
 	
-	public DataHandlerDescriptor(ResourceLocation identifier, Supplier<DataHandler> instancer, boolean sendOnJoin){
+	public DataHandlerDescriptor(ResourceLocation identifier, Supplier<DataHandler> instancer, boolean sendOnJoin, boolean sendBeforeEnter){
-		this(identifier, instancer, instancer, sendOnJoin);
+		this(identifier, instancer, instancer, sendOnJoin, sendBeforeEnter);
 	}
-	public DataHandlerDescriptor(ResourceLocation identifier, Supplier<DataHandler> receiv_instancer, Supplier<DataHandler> join_instancer, boolean sendOnJoin){
+	public DataHandlerDescriptor(ResourceLocation identifier, Supplier<DataHandler> receiv_instancer, Supplier<DataHandler> join_instancer, boolean sendOnJoin, boolean sendBeforeEnter){
 		this.INSTANCE = receiv_instancer;
 		this.JOIN_INSTANCE = join_instancer;
 		this.IDENTIFIER = identifier;
 		
 		this.sendOnJoin = sendOnJoin;
+		this.sendBeforeEnter = sendBeforeEnter;
 	}
 	
 	public final boolean sendOnJoin;
+	public final boolean sendBeforeEnter;
 	public final ResourceLocation IDENTIFIER;
 	public final Supplier<DataHandler> INSTANCE;
 	public final Supplier<DataHandler> JOIN_INSTANCE;

src/main/java/ru/bclib/api/dataexchange/handler/HelloClient.java

@@ -27,7 +27,7 @@ import java.util.Optional;
 import java.util.function.Consumer;
 
 public class HelloClient extends DataHandler {
-	public static DataHandlerDescriptor DESCRIPTOR = new DataHandlerDescriptor(new ResourceLocation(BCLib.MOD_ID, "hello_client"), HelloClient::new, true);
+	public static DataHandlerDescriptor DESCRIPTOR = new DataHandlerDescriptor(new ResourceLocation(BCLib.MOD_ID, "hello_client"), HelloClient::new, false, false);
 	
 	public HelloClient() {
 		super(DESCRIPTOR.IDENTIFIER, true);
@@ -42,7 +42,7 @@ public class HelloClient extends DataHandler {
 		return "0.0.0";
 	}
 	
-	protected static String getBCLibVersion(){
+	static String getBCLibVersion(){
 		return getModVersion(BCLib.MOD_ID);
 	}
 	
@@ -64,7 +64,7 @@ public class HelloClient extends DataHandler {
 	@Override
 	protected void runOnGameThread(Minecraft client, MinecraftServer server, boolean isClient) {
 		String localBclibVersion = getBCLibVersion();
-		BCLib.LOGGER.info("Hello Client received from BCLib. (client="+localBclibVersion+", server="+bclibVersion+")");
+		BCLib.LOGGER.info("Received Hello from Server. (client="+localBclibVersion+", server="+bclibVersion+")");
 		
 		if (DataFixerAPI.getModVersion(localBclibVersion) == DataFixerAPI.getModVersion(bclibVersion)){
 			showBCLibError(client);

src/main/java/ru/bclib/api/dataexchange/handler/HelloServer.java

@@ -0,0 +1,37 @@
+package ru.bclib.api.dataexchange.handler;
+
+import net.fabricmc.fabric.api.networking.v1.PacketSender;
+import net.minecraft.client.Minecraft;
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.MinecraftServer;
+import ru.bclib.BCLib;
+import ru.bclib.api.dataexchange.DataHandler;
+import ru.bclib.api.dataexchange.DataHandlerDescriptor;
+import ru.bclib.api.datafixer.DataFixerAPI;
+
+public class HelloServer extends DataHandler {
+	public static DataHandlerDescriptor DESCRIPTOR = new DataHandlerDescriptor(new ResourceLocation(BCLib.MOD_ID, "hello_server"), HelloServer::new, false, true);
+	
+	protected String bclibVersion ="0.0.0";
+	public HelloServer() {
+		super(DESCRIPTOR.IDENTIFIER, false);
+	}
+	
+	@Override
+	protected void deserializeFromIncomingData(FriendlyByteBuf buf, PacketSender responseSender, boolean fromClient) {
+		bclibVersion = DataFixerAPI.getModVersion(buf.readInt());
+	}
+	
+	@Override
+	protected void runOnGameThread(Minecraft client, MinecraftServer server, boolean isClient) {
+		String localBclibVersion = HelloClient.getBCLibVersion();
+		BCLib.LOGGER.info("Received Hello from Server. (server="+localBclibVersion+", client="+bclibVersion+")");
+		reply(new HelloClient(), server);
+	}
+	
+	@Override
+	protected void serializeData(FriendlyByteBuf buf) {
+		buf.writeInt(DataFixerAPI.getModVersion(HelloClient.getBCLibVersion()));
+	}
+}

src/main/java/ru/bclib/mixin/client/ClientLevelMixin.java

@@ -0,0 +1,2 @@
+package ru.bclib.mixin.client;public class ClientLevelMixin {
+}