Configuring Unreal Engine Networking Topology

In this lesson, you will learn how to configure a dedicated server environment to observe and validate data propagation patterns across multiple networked client instances.

The Dedicated Server Topology

While development often relies on "Listen Servers" (where one player acts as the host), a production-grade dedicated server topology decouples the simulation from any specific player's machine. In this model, the server runs a headless instance of the game, maintaining the "Source of Truth" for all Gameplay Tags, attributes, and Ability states, while clients act as thin terminals that predict and visualize the state.

To test this topology, you must configure your project to spawn multiple client instances connected to a single dedicated server.

Setting Up the Test Environment

1. In the Level Editor Toolbar, click the dropdown arrow next to Play.
2. Set Net Mode to Play as Dedicated Server.
3. Set Number of Players to 3 (or more).
4. Ensure Run Dedicated Server is checked.

When you trigger this, Unreal launches one dedicated server process and multiple game clients. Because you are already familiar with debugging Gameplay Tags and attribute synchronization, this environment is where you will finally see the "Replication Gap."

For example, when an ability is activated:

• The Server processes the logic and updates the AbilitySystemComponent (ASC).
• The Server then replicates the resulting changes to the Proxy ASCs on the clients.

You can observe this flow by using the net.IsServer check inside your OnRep functions or when debugging Gameplay Cues:

void AMyCharacter::OnRep_GameplayTags()
{
    Super::OnRep_GameplayTags();
    
    // Validate that the server state has arrived at the client instance
    if (!HasAuthority())
    {
        UE_LOG(LogTemp, Warning, TEXT("Client %d received updated tag state from Server."), GPlayInEditorID);
    }
}

By forcing this topology, you ensure that your GAS architecture doesn't rely on "Listen Server" quirks—such as the host's local authority—which often mask replication bugs that only surface when players connect over a true client-server boundary.

Key Takeaway: Testing in a dedicated server topology is the only way to guarantee your replication logic is decoupled from host-client authority and correctly handles the latency of multi-client data propagation.