Need help understanding networking code

Development Programming & Scripting C++
1

I came across a code pattern many times while going through the shooter project. But I am not sure yet what exactly does it do.


void AShooterWeapon::StartFire()
{
	if (Role < ROLE_Authority)
	{
		ServerStartFire();
	}

	if (!bWantsToFire)
	{
		bWantsToFire = true;
		DetermineWeaponState();
	}
}



bool AShooterWeapon::ServerStartFire_Validate()
{
	return true;
}

void AShooterWeapon::ServerStartFire_Implementation()
{
	StartFire();
}

Basically a as much as I could understand, this functions verifies from the server and calls a server version of that function.

But after a chain of functions, it calls this


void AShooterWeapon::HandleFiring()
{
	if ((CurrentAmmoInClip > 0 || HasInfiniteClip() || HasInfiniteAmmo()) && CanFire())
	{
		if (GetNetMode() != NM_DedicatedServer)
		{
			SimulateWeaponFire();
		}

		if (MyPawn && MyPawn->IsLocallyControlled())
		{
			FireWeapon();

			UseAmmo();
			
			// update firing FX on remote clients if function was called on server
			BurstCounter++;
		}
	}
	else if (CanReload())
	{
		StartReload();
	}
	else if (MyPawn && MyPawn->IsLocallyControlled())
	{
		if (GetCurrentAmmo() == 0 && !bRefiring)
		{
			PlayWeaponSound(OutOfAmmoSound);
			AShooterPlayerController* MyPC = Cast<AShooterPlayerController>(MyPawn->Controller);
			AShooterHUD* MyHUD = MyPC ? Cast<AShooterHUD>(MyPC->GetHUD()) : NULL;
			if (MyHUD)
			{
				MyHUD->NotifyOutOfAmmo();
			}
		}
		
		// stop weapon fire FX, but stay in Firing state
		if (BurstCounter > 0)
		{
			OnBurstFinished();
		}
	}

	if (MyPawn && MyPawn->IsLocallyControlled())
	{
		// local client will notify server
		if (Role < ROLE_Authority)
		{
			ServerHandleFiring();
		}

		// reload after firing last round
		if (CurrentAmmoInClip <= 0 && CanReload())
		{
			StartReload();
		}

		// setup refire timer
		bRefiring = (CurrentState == EWeaponState::Firing && WeaponConfig.TimeBetweenShots > 0.0f);
		if (bRefiring)
		{
			GetWorldTimerManager().SetTimer(this, &AShooterWeapon::HandleFiring, WeaponConfig.TimeBetweenShots, false);
		}
	}

	LastFireTime = GetWorld()->GetTimeSeconds();
}

bool AShooterWeapon::ServerHandleFiring_Validate()
{
	return true;
}

void AShooterWeapon::ServerHandleFiring_Implementation()
{
	const bool bShouldUpdateAmmo = (CurrentAmmoInClip > 0 && CanFire());

	HandleFiring();

	if (bShouldUpdateAmmo)
	{
		// update ammo
		UseAmmo();

		// update firing FX on remote clients
		BurstCounter++;
	}
}

I am really confused about what exactly does this do.

Whay does the ServerHandleFiring_Implementation() change the ammo and burst counter?

2

Handlefiring deals with them only if its the local player.



if (MyPawn && MyPawn->IsLocallyControlled())
		{
			FireWeapon();

			UseAmmo();
			
			// update firing FX on remote clients if function was called on server
			BurstCounter++;
		}

This is so you instantly see the counters change even in a really laggy game. If that werent the case, the client wouldnt see the counter change until the server managed to get the message to them. Imagine firing 3 or 4 times before you actually see your ammo counter drop.

So clients get instant updates, (yey!), but the problem is the server is in charge of the counters, so the _Implementation method also updates them so everyone is back in sync. Server updates all references to those counters which on the client happens to be the same value so they never see the change.

clever eh :smiley:

3

Where is the function ServerStartFire() in engine source code?