void RegisterMessage ( [EPixelStreamingMessageDirection](API\Plugins\PixelStreamingInput\EPixelStreamingMessageDirection) MessageDirection, const [FString](API\Runtime\Core\Containers\FString) & MessageType, [FPixelStreamingInputMessage](API\Plugins\PixelStreamingInput\FPixelStreamingInputMessage) Message, const [TFunction](API\Runtime\Core\GenericPlatform\TFunction)< void([FMemoryReader](API\Runtime\Core\Serialization\FMemoryReader))> & Handler )