From 3ccaaeac35d90c54ba9490d81289e6e9a39d0dd3 Mon Sep 17 00:00:00 2001
From: Marc Hermans <marc.hermans@ldtteam.com>
Date: Mon, 13 Nov 2023 23:42:46 +0100
Subject: [PATCH] Add support packetflow based payload handling. Add packet
 registration for registry packets.

---
 .../network/protocol/PacketFlow.java.patch    | 10 +++
 .../extensions/IPacketFlowExtension.java      | 18 +++++
 .../network/NetworkInitialization.java        | 24 +++++-
 .../network/configuration/SyncRegistries.java |  5 +-
 .../VanillaConnectionNetworkFilter.java       | 15 ++--
 .../handlers/ServerForgeRegistryHandler.java  |  8 +-
 .../payload/FrozenRegistryPayload.java        |  3 +-
 .../FrozenRegistrySyncCompletePayload.java    |  7 +-
 .../FrozenRegistrySyncCompletedPayload.java   | 21 ------
 .../FrozenRegistrySyncStartPayload.java       |  3 +-
 .../network/payload/SplitPacketPayload.java   |  6 +-
 .../ConfigurationPayloadHandler.java          | 52 +++++++++++++
 .../registrar/IFlowBasedPayloadRegistrar.java | 11 +++
 .../registrar/IPayloadRegistrar.java          | 75 +++++++++++++++++++
 .../registrar/ModdedPacketRegistrar.java      | 11 +++
 .../registrar/PayloadHandlerBuilder.java      | 40 ++++++++++
 .../registrar/PlayPayloadHandler.java         | 52 +++++++++++++
 .../neoforge/registries/RegistryManager.java  |  4 +-
 18 files changed, 319 insertions(+), 46 deletions(-)
 create mode 100644 patches/net/minecraft/network/protocol/PacketFlow.java.patch
 create mode 100644 src/main/java/net/neoforged/neoforge/common/extensions/IPacketFlowExtension.java
 delete mode 100644 src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletedPayload.java
 create mode 100644 src/main/java/net/neoforged/neoforge/network/registration/registrar/ConfigurationPayloadHandler.java
 create mode 100644 src/main/java/net/neoforged/neoforge/network/registration/registrar/PayloadHandlerBuilder.java
 create mode 100644 src/main/java/net/neoforged/neoforge/network/registration/registrar/PlayPayloadHandler.java

diff --git a/patches/net/minecraft/network/protocol/PacketFlow.java.patch b/patches/net/minecraft/network/protocol/PacketFlow.java.patch
new file mode 100644
index 00000000000..b6e9dd90f2a
--- /dev/null
+++ b/patches/net/minecraft/network/protocol/PacketFlow.java.patch
@@ -0,0 +1,10 @@
+--- a/net/minecraft/network/protocol/PacketFlow.java
++++ b/net/minecraft/network/protocol/PacketFlow.java
+@@ -1,6 +1,6 @@
+ package net.minecraft.network.protocol;
+ 
+-public enum PacketFlow {
++public enum PacketFlow implements net.neoforged.neoforge.common.extensions.IPacketFlowExtension {
+    SERVERBOUND,
+    CLIENTBOUND;
+ 
diff --git a/src/main/java/net/neoforged/neoforge/common/extensions/IPacketFlowExtension.java b/src/main/java/net/neoforged/neoforge/common/extensions/IPacketFlowExtension.java
new file mode 100644
index 00000000000..c0a25183e6b
--- /dev/null
+++ b/src/main/java/net/neoforged/neoforge/common/extensions/IPacketFlowExtension.java
@@ -0,0 +1,18 @@
+package net.neoforged.neoforge.common.extensions;
+
+import net.minecraft.network.protocol.PacketFlow;
+
+public interface IPacketFlowExtension {
+
+    default PacketFlow self() {
+        return (PacketFlow) this;
+    }
+    
+    default boolean isClientbound() {
+        return self() == PacketFlow.CLIENTBOUND;
+    }
+    
+    default boolean isServerbound() {
+        return self() == PacketFlow.SERVERBOUND;
+    }
+}
diff --git a/src/main/java/net/neoforged/neoforge/network/NetworkInitialization.java b/src/main/java/net/neoforged/neoforge/network/NetworkInitialization.java
index 7f63974cc1c..818ad4c1988 100644
--- a/src/main/java/net/neoforged/neoforge/network/NetworkInitialization.java
+++ b/src/main/java/net/neoforged/neoforge/network/NetworkInitialization.java
@@ -8,12 +8,19 @@
 import java.util.Arrays;
 import java.util.List;
 
+import net.minecraft.network.protocol.PacketFlow;
 import net.neoforged.bus.api.SubscribeEvent;
 import net.neoforged.fml.common.Mod;
 import net.neoforged.neoforge.internal.versions.neoforge.NeoForgeVersion;
 import net.neoforged.neoforge.network.event.EventNetworkChannel;
 import net.neoforged.neoforge.network.event.RegisterPacketHandlerEvent;
+import net.neoforged.neoforge.network.handlers.ClientForgeRegistryHandler;
+import net.neoforged.neoforge.network.handlers.ServerForgeRegistryHandler;
+import net.neoforged.neoforge.network.handling.ConfigurationPayloadContext;
+import net.neoforged.neoforge.network.handling.IConfigurationPayloadHandler;
 import net.neoforged.neoforge.network.payload.FrozenRegistryPayload;
+import net.neoforged.neoforge.network.payload.FrozenRegistrySyncCompletePayload;
+import net.neoforged.neoforge.network.payload.FrozenRegistrySyncStartPayload;
 import net.neoforged.neoforge.network.simple.SimpleChannel;
 import net.neoforged.neoforge.registries.RegistryManager;
 import org.jetbrains.annotations.ApiStatus;
@@ -26,12 +33,27 @@ public class NetworkInitialization {
     public static void register(final RegisterPacketHandlerEvent event) {
         event.registrar()
                 .withVersion(buildNetworkVersion())
+                .flowing(PacketFlow.CLIENTBOUND)
+                .configuration(
+                        FrozenRegistrySyncStartPayload.ID,
+                        FrozenRegistrySyncStartPayload.class,
+                        FrozenRegistrySyncStartPayload::new,
+                        handlers -> handlers.client(ClientForgeRegistryHandler.getInstance()::handle)
+                )
                 .configuration(
                         FrozenRegistryPayload.ID,
                         FrozenRegistryPayload.class,
                         FrozenRegistryPayload::new,
-                        
+                        handlers -> handlers.client(ClientForgeRegistryHandler.getInstance()::handle)
                 )
+                .bidirectional()
+                .configuration(
+                        FrozenRegistrySyncCompletePayload.ID,
+                        FrozenRegistrySyncCompletePayload.class,
+                        FrozenRegistrySyncCompletePayload::new,
+                        handlers -> handlers.client(ClientForgeRegistryHandler.getInstance()::handle)
+                                            .server(ServerForgeRegistryHandler.getInstance()::handle)
+                );
     }
     
     /**
diff --git a/src/main/java/net/neoforged/neoforge/network/configuration/SyncRegistries.java b/src/main/java/net/neoforged/neoforge/network/configuration/SyncRegistries.java
index ffc40a6c324..1ab89b4db6b 100644
--- a/src/main/java/net/neoforged/neoforge/network/configuration/SyncRegistries.java
+++ b/src/main/java/net/neoforged/neoforge/network/configuration/SyncRegistries.java
@@ -1,9 +1,8 @@
 package net.neoforged.neoforge.network.configuration;
 
-import net.minecraft.network.protocol.Packet;
 import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
-import net.minecraft.server.network.ConfigurationTask;
 import net.neoforged.neoforge.network.payload.FrozenRegistrySyncStartPayload;
+import net.neoforged.neoforge.registries.RegistryManager;
 
 import java.util.function.Consumer;
 
@@ -13,7 +12,7 @@ public record SyncRegistries() implements ICustomConfigurationTask {
     
     @Override
     public void run(Consumer<CustomPacketPayload> sender) {
-        sender.accept(new FrozenRegistrySyncStartPayload());
+        sender.accept(new FrozenRegistrySyncStartPayload(RegistryManager.getRegistryNamesForSyncToClient()));
     }
     
     @Override
diff --git a/src/main/java/net/neoforged/neoforge/network/filters/VanillaConnectionNetworkFilter.java b/src/main/java/net/neoforged/neoforge/network/filters/VanillaConnectionNetworkFilter.java
index 9c5511eec9a..31909cf424a 100644
--- a/src/main/java/net/neoforged/neoforge/network/filters/VanillaConnectionNetworkFilter.java
+++ b/src/main/java/net/neoforged/neoforge/network/filters/VanillaConnectionNetworkFilter.java
@@ -9,11 +9,6 @@
 import com.mojang.brigadier.tree.RootCommandNode;
 import com.mojang.logging.LogUtils;
 import io.netty.channel.ChannelHandler;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-import java.util.function.BiConsumer;
-import java.util.stream.Collectors;
 import net.minecraft.commands.CommandBuildContext;
 import net.minecraft.commands.Commands;
 import net.minecraft.commands.SharedSuggestionProvider;
@@ -32,12 +27,18 @@
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.tags.TagNetworkSerialization;
-import net.neoforged.neoforge.network.NetworkHooks;
+import net.neoforged.neoforge.network.registration.NetworkRegistry;
 import net.neoforged.neoforge.registries.ForgeRegistries;
 import net.neoforged.neoforge.registries.RegistryManager;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.function.BiConsumer;
+import java.util.stream.Collectors;
+
 /**
  * A filter for impl packets, used to filter/modify parts of vanilla impl messages that
  * will cause errors or warnings on vanilla clients, for example entity attributes that are added by Forge or mods.
@@ -57,7 +58,7 @@ public VanillaConnectionNetworkFilter() {
 
     @Override
     protected boolean isNecessary(Connection manager) {
-        return NetworkHooks.isVanillaConnection(manager);
+        return NetworkRegistry.getInstance().isVanillaConnection(manager);
     }
 
     /**
diff --git a/src/main/java/net/neoforged/neoforge/network/handlers/ServerForgeRegistryHandler.java b/src/main/java/net/neoforged/neoforge/network/handlers/ServerForgeRegistryHandler.java
index 4938eb53462..d31e923fd39 100644
--- a/src/main/java/net/neoforged/neoforge/network/handlers/ServerForgeRegistryHandler.java
+++ b/src/main/java/net/neoforged/neoforge/network/handlers/ServerForgeRegistryHandler.java
@@ -1,8 +1,8 @@
 package net.neoforged.neoforge.network.handlers;
 
+import net.neoforged.neoforge.network.configuration.SyncRegistries;
 import net.neoforged.neoforge.network.handling.ConfigurationPayloadContext;
-import net.neoforged.neoforge.network.handling.IConfigurationPayloadHandler;
-import net.neoforged.neoforge.network.payload.FrozenRegistrySyncCompletedPayload;
+import net.neoforged.neoforge.network.payload.FrozenRegistrySyncCompletePayload;
 
 public class ServerForgeRegistryHandler {
     
@@ -15,7 +15,7 @@ public static ServerForgeRegistryHandler getInstance() {
     private ServerForgeRegistryHandler() {
     }
     
-    public void handle(ConfigurationPayloadContext context, FrozenRegistrySyncCompletedPayload payload) {
-        context.taskCompletedHandler().onTaskCompleted();
+    public void handle(ConfigurationPayloadContext context, FrozenRegistrySyncCompletePayload payload) {
+        context.taskCompletedHandler().onTaskCompleted(SyncRegistries.TYPE);
     }
 }
diff --git a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistryPayload.java b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistryPayload.java
index 99949a26741..3826861a5eb 100644
--- a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistryPayload.java
+++ b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistryPayload.java
@@ -3,13 +3,14 @@
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
 import net.minecraft.resources.ResourceLocation;
+import net.neoforged.neoforge.network.reading.PayloadReadingContext;
 import net.neoforged.neoforge.registries.ForgeRegistry;
 
 public record FrozenRegistryPayload(ResourceLocation registryName, ForgeRegistry.Snapshot snapshot) implements CustomPacketPayload {
     
     public static final ResourceLocation ID = new ResourceLocation("neoforge:frozen_registry");
     
-    public FrozenRegistryPayload(FriendlyByteBuf buf) {
+    public FrozenRegistryPayload(FriendlyByteBuf buf, PayloadReadingContext context) {
         this(buf.readResourceLocation(), ForgeRegistry.Snapshot.read(buf));
     }
     
diff --git a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletePayload.java b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletePayload.java
index 1f1e4bace42..b607a052a55 100644
--- a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletePayload.java
+++ b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletePayload.java
@@ -3,11 +3,16 @@
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
 import net.minecraft.resources.ResourceLocation;
+import net.neoforged.neoforge.network.reading.PayloadReadingContext;
 import org.jetbrains.annotations.NotNull;
 
 public record FrozenRegistrySyncCompletePayload() implements CustomPacketPayload {
     
-    private static final ResourceLocation ID = new ResourceLocation("neoforge:frozen_registry_sync_complete");
+    public static final ResourceLocation ID = new ResourceLocation("neoforge:frozen_registry_sync_complete");
+    
+    public FrozenRegistrySyncCompletePayload(FriendlyByteBuf buf, PayloadReadingContext context) {
+        this();
+    }
     
     @Override
     public void write(@NotNull FriendlyByteBuf buf) {
diff --git a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletedPayload.java b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletedPayload.java
deleted file mode 100644
index cd949f2a633..00000000000
--- a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncCompletedPayload.java
+++ /dev/null
@@ -1,21 +0,0 @@
-package net.neoforged.neoforge.network.payload;
-
-import net.minecraft.network.FriendlyByteBuf;
-import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
-import net.minecraft.resources.ResourceLocation;
-import org.jetbrains.annotations.NotNull;
-
-public record FrozenRegistrySyncCompletedPayload() implements CustomPacketPayload {
-    
-    public static final ResourceLocation ID = new ResourceLocation("neoforge:frozen_registry_sync_completed");
-    
-    @Override
-    public void write(@NotNull FriendlyByteBuf p_294947_) {
-    
-    }
-    
-    @Override
-    public @NotNull ResourceLocation id() {
-        return ID;
-    }
-}
diff --git a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncStartPayload.java b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncStartPayload.java
index 8fa32c06f4d..eabd59fa0f8 100644
--- a/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncStartPayload.java
+++ b/src/main/java/net/neoforged/neoforge/network/payload/FrozenRegistrySyncStartPayload.java
@@ -3,6 +3,7 @@
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
 import net.minecraft.resources.ResourceLocation;
+import net.neoforged.neoforge.network.reading.PayloadReadingContext;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Set;
@@ -11,7 +12,7 @@ public record FrozenRegistrySyncStartPayload(Set<ResourceLocation> toAccess) imp
     
     public static final ResourceLocation ID = new ResourceLocation("neoforge:frozen_registry_sync_start");
     
-    public FrozenRegistrySyncStartPayload(FriendlyByteBuf buf) {
+    public FrozenRegistrySyncStartPayload(FriendlyByteBuf buf, PayloadReadingContext context) {
         this(buf.readSet(FriendlyByteBuf::readResourceLocation));
     }
     
diff --git a/src/main/java/net/neoforged/neoforge/network/payload/SplitPacketPayload.java b/src/main/java/net/neoforged/neoforge/network/payload/SplitPacketPayload.java
index a36abc4e234..4dc530d0acd 100644
--- a/src/main/java/net/neoforged/neoforge/network/payload/SplitPacketPayload.java
+++ b/src/main/java/net/neoforged/neoforge/network/payload/SplitPacketPayload.java
@@ -9,12 +9,8 @@ public record SplitPacketPayload(byte[] payload) implements CustomPacketPayload
     
     public static final ResourceLocation ID = new ResourceLocation("neoforge", "split");
     
-    public SplitPacketPayload(FriendlyByteBuf buf) {
-        this(buf.readBytes(buf.readVarInt()).array());
-    }
-    
     public SplitPacketPayload(FriendlyByteBuf buf, PayloadReadingContext context) {
-        this(buf);
+        this(buf.readBytes(buf.readVarInt()).array());
     }
     
     @Override
diff --git a/src/main/java/net/neoforged/neoforge/network/registration/registrar/ConfigurationPayloadHandler.java b/src/main/java/net/neoforged/neoforge/network/registration/registrar/ConfigurationPayloadHandler.java
new file mode 100644
index 00000000000..9cfe7c46614
--- /dev/null
+++ b/src/main/java/net/neoforged/neoforge/network/registration/registrar/ConfigurationPayloadHandler.java
@@ -0,0 +1,52 @@
+package net.neoforged.neoforge.network.registration.registrar;
+
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.neoforged.neoforge.network.handling.ConfigurationPayloadContext;
+import net.neoforged.neoforge.network.handling.IConfigurationPayloadHandler;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public final class ConfigurationPayloadHandler<T extends CustomPacketPayload> implements IConfigurationPayloadHandler<T> {
+    
+    @Nullable
+    private final IConfigurationPayloadHandler<T> clientSide;
+    @Nullable
+    private final IConfigurationPayloadHandler<T> serverSide;
+    
+    private ConfigurationPayloadHandler(@Nullable IConfigurationPayloadHandler<T> clientSide, @Nullable IConfigurationPayloadHandler<T> serverSide) {
+        this.clientSide = clientSide;
+        this.serverSide = serverSide;
+    }
+    
+    @Override
+    public void handle(ConfigurationPayloadContext context, T payload) {
+        if (context.flow().isClientbound()) {
+            if (clientSide != null) {
+                clientSide.handle(context, payload);
+            }
+        } else if (context.flow().isServerbound()) {
+            if (serverSide != null) {
+                serverSide.handle(context, payload);
+            }
+        }
+    }
+    
+    public static class Builder<T extends CustomPacketPayload> {
+        private @Nullable IConfigurationPayloadHandler<T> clientSide;
+        private @Nullable IConfigurationPayloadHandler<T> serverSide;
+        
+        public Builder<T> client(@NotNull IConfigurationPayloadHandler<T> clientSide) {
+            this.clientSide = clientSide;
+            return this;
+        }
+        
+        public Builder<T> server(@NotNull IConfigurationPayloadHandler<T> serverSide) {
+            this.serverSide = serverSide;
+            return this;
+        }
+        
+        ConfigurationPayloadHandler<T> create() {
+            return new ConfigurationPayloadHandler<T>(clientSide, serverSide);
+        }
+    }
+}
diff --git a/src/main/java/net/neoforged/neoforge/network/registration/registrar/IFlowBasedPayloadRegistrar.java b/src/main/java/net/neoforged/neoforge/network/registration/registrar/IFlowBasedPayloadRegistrar.java
index 63fc2a989d4..40caa089b67 100644
--- a/src/main/java/net/neoforged/neoforge/network/registration/registrar/IFlowBasedPayloadRegistrar.java
+++ b/src/main/java/net/neoforged/neoforge/network/registration/registrar/IFlowBasedPayloadRegistrar.java
@@ -14,4 +14,15 @@ public interface IFlowBasedPayloadRegistrar extends IPayloadRegistrar {
      * @return A registrar that is bound to the given flow.
      */
     IPayloadRegistrarWithAcceptableRange flowing(PacketFlow flow);
+    
+    /**
+     * Enables payloads registered with this registrar to flow in both directions.
+     * <p>
+     *     This is the default value for all registrars, unless {@link #flowing(PacketFlow)} has been called.
+     *     Invoking this method as such is only needed to reset the ability to flow in both directions.
+     * </p>
+     *
+     * @return A registrar that is bound to both directions.
+     */
+    IPayloadRegistrarWithAcceptableRange bidirectional();
 }
diff --git a/src/main/java/net/neoforged/neoforge/network/registration/registrar/IPayloadRegistrar.java b/src/main/java/net/neoforged/neoforge/network/registration/registrar/IPayloadRegistrar.java
index 395c68d0461..a28cb62515c 100644
--- a/src/main/java/net/neoforged/neoforge/network/registration/registrar/IPayloadRegistrar.java
+++ b/src/main/java/net/neoforged/neoforge/network/registration/registrar/IPayloadRegistrar.java
@@ -7,6 +7,8 @@
 import net.neoforged.neoforge.network.handling.*;
 import net.neoforged.neoforge.network.reading.IPayloadReader;
 
+import java.util.function.Consumer;
+
 /**
  * Defines a registrar for custom payloads that can be sent over the network.
  * <p>
@@ -85,6 +87,31 @@ public interface IPayloadRegistrar {
      */
     <T extends CustomPacketPayload> IPayloadRegistrarWithAcceptableRange play(ResourceLocation id, Class<T> type, IPayloadReader<T> reader, IPlayPayloadHandler<T> handler);
     
+    /**
+     * Registers a new payload type for the play phase.
+     * <p>
+     *     This method allows different handlers to be registered for different packet-flows.
+     *     <br>
+     *     In practice this means that you can register a different handler for clientbound and serverbound packets,
+     *     which allows you to handle them differently on the client and server side.
+     * </p>
+     *
+     * @param id The id of the payload.
+     * @param type The class of the payload.
+     * @param reader The reader for the payload.
+     * @param handler The handler for the payload.
+     * @param <T> The type of the payload.
+     * @return The registrar.
+     *
+     * @implNote This method will capture all internal errors and wrap them in a {@link RegistrationFailedException}.
+     */
+    default <T extends CustomPacketPayload> IPayloadRegistrarWithAcceptableRange play(ResourceLocation id, Class<T> type, IPayloadReader<T> reader, Consumer<PlayPayloadHandler.Builder<T>> handler) {
+        final PlayPayloadHandler.Builder<T> builder = new PlayPayloadHandler.Builder<>();
+        handler.accept(builder);
+        return play(id, type, reader, builder.create());
+    }
+    
+    
     /**
      * Registers a new payload type for the configuration phase.
      *
@@ -99,6 +126,30 @@ public interface IPayloadRegistrar {
      */
     <T extends CustomPacketPayload> IPayloadRegistrarWithAcceptableRange configuration(ResourceLocation id, Class<T> type, IPayloadReader<T> reader, IConfigurationPayloadHandler<T> handler);
     
+    /**
+     * Registers a new payload type for the configuration phase.
+     * <p>
+     *     This method allows different handlers to be registered for different packet-flows.
+     *     <br>
+     *     In practice this means that you can register a different handler for clientbound and serverbound packets,
+     *     which allows you to handle them differently on the client and server side.
+     * </p>
+     *
+     * @param id The id of the payload.
+     * @param type The class of the payload.
+     * @param reader The reader for the payload.
+     * @param handler The handler for the payload.
+     * @param <T> The type of the payload.
+     * @return The registrar.
+     *
+     * @implNote This method will capture all internal errors and wrap them in a {@link RegistrationFailedException}.
+     */
+    default <T extends CustomPacketPayload> IPayloadRegistrarWithAcceptableRange configuration(ResourceLocation id, Class<T> type, IPayloadReader<T> reader, Consumer<ConfigurationPayloadHandler.Builder<T>> handler) {
+        final ConfigurationPayloadHandler.Builder<T> builder = new ConfigurationPayloadHandler.Builder<>();
+        handler.accept(builder);
+        return configuration(id, type, reader, builder.create());
+    }
+    
     /**
      * Registers a new payload type for all supported phases.
      *
@@ -113,4 +164,28 @@ public interface IPayloadRegistrar {
     default <T extends CustomPacketPayload> IPayloadRegistrarWithAcceptableRange common(ResourceLocation id, Class<T> type, IPayloadReader<T> reader, IPayloadHandler<T> handler) {
         return play(id, type, reader, handler::handle).configuration(id, type, reader, handler::handle);
     }
+    
+    /**
+     * Registers a new payload type for all supported phases.
+     * <p>
+     *     This method allows different handlers to be registered for different packet-flows.
+     *     <br>
+     *     In practice this means that you can register a different handler for clientbound and serverbound packets,
+     *     which allows you to handle them differently on the client and server side.
+     * </p>
+     *
+     * @param id The id of the payload.
+     * @param type The class of the payload.
+     * @param reader The reader for the payload.
+     * @param handler The handler for the payload.
+     * @return The registrar.
+     *
+     * @param <T> The type of the payload.
+     */
+    default <T extends CustomPacketPayload> IPayloadRegistrarWithAcceptableRange common(ResourceLocation id, Class<T> type, IPayloadReader<T> reader, Consumer<PayloadHandlerBuilder<T>> handler) {
+        final PayloadHandlerBuilder<T> builder = new PayloadHandlerBuilder<>();
+        handler.accept(builder);
+        
+        return play(id, type, reader, builder::handle).configuration(id, type, reader, builder::handle);
+    }
 }
diff --git a/src/main/java/net/neoforged/neoforge/network/registration/registrar/ModdedPacketRegistrar.java b/src/main/java/net/neoforged/neoforge/network/registration/registrar/ModdedPacketRegistrar.java
index 832c7fca8c0..85a4aa964f4 100644
--- a/src/main/java/net/neoforged/neoforge/network/registration/registrar/ModdedPacketRegistrar.java
+++ b/src/main/java/net/neoforged/neoforge/network/registration/registrar/ModdedPacketRegistrar.java
@@ -86,6 +86,11 @@ public IPayloadRegistrarWithAcceptableRange flowing(PacketFlow flow) {
         return configured.flowing(flow);
     }
     
+    @Override
+    public IPayloadRegistrarWithAcceptableRange bidirectional() {
+        return this;
+    }
+    
     private void configuration(final ResourceLocation id, ConfigurationRegistration<?> registration) {
         validatePayload(id, registration.type(), configurationPayloads);
         
@@ -171,6 +176,12 @@ public IPayloadRegistrarWithAcceptableRange flowing(PacketFlow flow) {
             this.flow = flow;
             return this;
         }
+        
+        @Override
+        public IPayloadRegistrarWithAcceptableRange bidirectional() {
+            this.flow = null;
+            return this;
+        }
     }
     
 }
diff --git a/src/main/java/net/neoforged/neoforge/network/registration/registrar/PayloadHandlerBuilder.java b/src/main/java/net/neoforged/neoforge/network/registration/registrar/PayloadHandlerBuilder.java
new file mode 100644
index 00000000000..2164134ec09
--- /dev/null
+++ b/src/main/java/net/neoforged/neoforge/network/registration/registrar/PayloadHandlerBuilder.java
@@ -0,0 +1,40 @@
+package net.neoforged.neoforge.network.registration.registrar;
+
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.neoforged.neoforge.network.handling.IPayloadContext;
+import net.neoforged.neoforge.network.handling.IPayloadHandler;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public class PayloadHandlerBuilder<T extends CustomPacketPayload> {
+    private @Nullable IPayloadHandler<T> clientSide;
+    private @Nullable IPayloadHandler<T> serverSide;
+    
+    public PayloadHandlerBuilder<T> client(@NotNull IPayloadHandler<T> clientSide) {
+        this.clientSide = clientSide;
+        return this;
+    }
+    
+    public PayloadHandlerBuilder<T> server(@NotNull IPayloadHandler<T> serverSide) {
+        this.serverSide = serverSide;
+        return this;
+    }
+    
+    void handle(PlayPayloadHandler.Builder<T> play) {
+        if (clientSide != null) {
+            play.client(clientSide::handle);
+        }
+        if (serverSide != null) {
+            play.server(serverSide::handle);
+        }
+    }
+    
+    void handle(ConfigurationPayloadHandler.Builder<T> configuration) {
+        if (clientSide != null) {
+            configuration.client(clientSide::handle);
+        }
+        if (serverSide != null) {
+            configuration.server(serverSide::handle);
+        }
+    }
+}
diff --git a/src/main/java/net/neoforged/neoforge/network/registration/registrar/PlayPayloadHandler.java b/src/main/java/net/neoforged/neoforge/network/registration/registrar/PlayPayloadHandler.java
new file mode 100644
index 00000000000..f79dd617b38
--- /dev/null
+++ b/src/main/java/net/neoforged/neoforge/network/registration/registrar/PlayPayloadHandler.java
@@ -0,0 +1,52 @@
+package net.neoforged.neoforge.network.registration.registrar;
+
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.neoforged.neoforge.network.handling.IPlayPayloadHandler;
+import net.neoforged.neoforge.network.handling.PlayPayloadContext;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public final class PlayPayloadHandler<T extends CustomPacketPayload> implements IPlayPayloadHandler<T> {
+    
+    @Nullable
+    private final IPlayPayloadHandler<T> clientSide;
+    @Nullable
+    private final IPlayPayloadHandler<T> serverSide;
+    
+    private PlayPayloadHandler(@Nullable IPlayPayloadHandler<T> clientSide, @Nullable IPlayPayloadHandler<T> serverSide) {
+        this.clientSide = clientSide;
+        this.serverSide = serverSide;
+    }
+    
+    @Override
+    public void handle(PlayPayloadContext context, T payload) {
+        if (context.flow().isClientbound()) {
+            if (clientSide != null) {
+                clientSide.handle(context, payload);
+            }
+        } else if (context.flow().isServerbound()) {
+            if (serverSide != null) {
+                serverSide.handle(context, payload);
+            }
+        }
+    }
+    
+    public static class Builder<T extends CustomPacketPayload> {
+        private @Nullable IPlayPayloadHandler<T> clientSide;
+        private @Nullable IPlayPayloadHandler<T> serverSide;
+        
+        public Builder<T> client(@NotNull IPlayPayloadHandler<T> clientSide) {
+            this.clientSide = clientSide;
+            return this;
+        }
+        
+        public Builder<T> server(@NotNull IPlayPayloadHandler<T> serverSide) {
+            this.serverSide = serverSide;
+            return this;
+        }
+        
+        PlayPayloadHandler<T> create() {
+            return new PlayPayloadHandler<T>(clientSide, serverSide);
+        }
+    }
+}
diff --git a/src/main/java/net/neoforged/neoforge/registries/RegistryManager.java b/src/main/java/net/neoforged/neoforge/registries/RegistryManager.java
index d1e3218bdb4..6267f8bc7f7 100644
--- a/src/main/java/net/neoforged/neoforge/registries/RegistryManager.java
+++ b/src/main/java/net/neoforged/neoforge/registries/RegistryManager.java
@@ -169,8 +169,8 @@ public static List<FrozenRegistryPayload> generateRegistryPackets(boolean isLoca
                        : Collections.emptyList();
     }
 
-    public static List<ResourceLocation> getRegistryNamesForSyncToClient() {
-        return ACTIVE.registries.keySet().stream().filter(resloc -> ACTIVE.synced.contains(resloc)).collect(Collectors.toList());
+    public static Set<ResourceLocation> getRegistryNamesForSyncToClient() {
+        return ACTIVE.registries.keySet().stream().filter(resloc -> ACTIVE.synced.contains(resloc)).collect(Collectors.toSet());
     }
 
     public static Set<ResourceLocation> getVanillaRegistryKeys() {