Strange Replication in C++

Development Programming & Scripting Multiplayer & Networking
1

I tried posting this on the UE4 AnswerHub herebut haven’t had any luck with responses. I’m rather new with UE4’s multiplayer and the workflow for replication.

Hello all,

I have a projectile that a player shoots, then on impact with another player it plays a “hit” sound.

The Pawn class calls a Server RPC HandleFire that spawns the projectile.


void ATechnomancyCharacter::HandleFire_Implementation() {
  ...
  GetWorld()->SpawnActor<ABaseAttack>(SpawnLocation, Direction.Rotation(), SpawnParameters);
  ...
}

Then the OnProjectileOverlap function of the projectile calls a Client RPC called PlayClientSound


void ABaseAttack::OnProjectileOverlap(UPrimitiveComponent* OverlappedComp, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult) {
  ...
  IGameObject* OtherObject = Cast<IGameObject>(OtherActor);
  IGameObject* InstigatorObject = Cast<IGameObject>(Instigator);
  ...
  if (OtherObject && InstigatorObject)
  {
    ...
    InstigatorObject->PlayClientSound(HitSound);
  }
  ...
}

Here is the Client RPC


void ATechnomancyCharacter::PlayClientSound_Implementation(USoundCue* Sound) {
  UGameplayStatics::PlaySound2D(GetWorld(), Sound);
}

So in a multiplayer setting (listen server) I get some strange replication issues. When I play as a client things work as intended (meaning when I hit another player I get the “Hit” sound), but when I play as the server I will get the sound but it will SOMETIMES also play the sound on the client which is obviously not wanted.

Is there something I am doing wrong with the RPC calls I am making to cause this?

2

There is no need to use a RPC at all. Assuming that you projectile is replicated, you can simply check for overlaps on client and server and play the sound autonomously.

3

I believe I was trying that before with not using a client RPC at all. The issue I was having there is that it was playing the sound for everyone.

So how can I make it so it only plays the sound for the player firing the projectile.

4

When spawning the projectile you set the correct owner (replicated by default, see Actor.h). Then in OnProjectileOverlap you only play the sound if the player is also the owner.

5

Okay that sounds reasonable. I will try that later today and post back with results.