Freelook

public class Example implements ModInitializer {
    @Override
    public void onInitialize() {
        PayloadTypeRegistry.clientboundPlay().register(DisableModPayload.TYPE, DisableModPayload.CODEC);
        PayloadTypeRegistry.serverboundPlay().register(HandshakePayload.TYPE, HandshakePayload.CODEC);

        ServerPlayNetworking.registerGlobalReceiver(HandshakePayload.TYPE,
                (payload, ctx) -> ServerPlayNetworking.send(ctx.player(), new DisableModPayload())
        );
    }

    public record DisableModPayload() implements CustomPacketPayload {
        public static final Type<DisableModPayload> TYPE = new Type<>(Identifier.parse("freelook:disable"));
        public static final StreamCodec<RegistryFriendlyByteBuf,  DisableModPayload> CODEC = StreamCodec.unit(new DisableModPayload());

        @Override
        public Type<? extends CustomPacketPayload> type() {
            return TYPE;
        }
    }

    public record HandshakePayload() implements CustomPacketPayload {
        public static final Type<HandshakePayload> TYPE = new Type<>(Identifier.parse("freelook:handshake"));
        public static final StreamCodec<RegistryFriendlyByteBuf, HandshakePayload> CODEC = StreamCodec.unit(new HandshakePayload());

        @Override
        public Type<? extends CustomPacketPayload> type() {
            return TYPE;
        }
    }
}