Networking

Sending data between client and server with custom payloads. Package: net.ixdarklord.coolcatcore.api.network.

Register every payload during construction (ModConstructor#onConstructMod()), on both sides.

Record payloads: no codec needed

If every component of a record payload is a type PayloadCodecs knows, CoolCatLib builds the StreamCodec for you:

public record PingPayload(BlockPos pos, List<String> tags, Optional<Component> note) implements CustomPacketPayload {
    public static final Type<PingPayload> TYPE = new Type<>(Identifier.fromNamespaceAndPath("mymod", "ping"));

    @Override
    public Type<PingPayload> type() { return TYPE; }
}

// onConstructMod():
Network.registerServerbound(PingPayload.class, (payload, context) -> {
    ServerPlayer sender = (ServerPlayer) context.getPlayer();
    // Runs on the main thread.
});

// On the client:
Network.sendToServer(new PingPayload(pos, List.of("a"), Optional.empty()));

The payload's Type is read from the record's single static Type field (or the one named TYPE). Registering a payload with a component type that has no codec throws right away, naming the component.

Types PayloadCodecs knows out of the box: - primitives and their boxes, String, byte[], long[], OptionalInt, UUID; - Identifier, BlockPos, ChunkPos, GlobalPos, Direction, Vec3, Vector3f, Quaternionf; - Component, ItemStack, CompoundTag, Tag, BlockState, Item, Block, EntityType; - built from their parts: enums, records, arrays, Optional, List/Collection, Set, Map, Either and ResourceKey.

Components can't be null; use Optional. Teach it other types with PayloadCodecs.register(MyType.class, codec), or registerFactory(...) for generic types.

With your own codec

Network.registerClientbound(MyPayload.TYPE, MyPayload.STREAM_CODEC, (payload, context) -> {
    // Client only; runs on the main thread.
});

Sending

Network.sendToServer(payload);                        // client → server
Network.sendToPlayer(serverPlayer, payload);          // server → one player
Network.sendToPlayers(server.getPlayerList().getPlayers(), payload);

// Players without your mod (and GameTest mock players) have no channel for it; NeoForge throws if you send anyway.
if (Network.canPlayerReceive(serverPlayer, MyPayload.TYPE)) Network.sendToPlayer(serverPlayer, payload);

Reference

Type	Description
Network	Register: registerServerbound(type, codec, receiver), registerClientbound(type, codec, receiver), and the record forms registerServerbound(Class, receiver), registerServerbound(Type, Class, receiver), registerClientbound(Class, receiver), registerClientbound(Type, Class, receiver). Send: sendToServer, sendToPlayer, sendToPlayers. canPlayerReceive(player, type).
PayloadReceiver<T>	receive(T payload, PacketContext context), called on the main thread.
PacketContext	getPlayer() (the sender on the server, the local player on the client), queue(Runnable), getEnvironment().
PayloadCodecs	register(Class<V>, StreamCodec), registerFactory(Class<?> rawType, Factory), forRecord(Class<R>), get(Type), has(Type).