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YetiTech Studios

Using Global Messenger

UGlobalMessageSubsystem decouples senders and receivers across your entire level. Terminal commands, programs, and world actors can broadcast and listen without direct references — the pattern used in the demo game to open a roof door from the in-world Terminal.

Full API details: Global Messenger Subsystem.

sequenceDiagram
  participant Cmd as UOperatingSystemTerminalCommand
  participant GM as UGlobalMessageSubsystem
  participant Door as BP_Door level actor
  Cmd->>GM: BroadcastMessage(gameplay tag, payload)
  GM->>Door: ListenToMessage callback
  Door->>Door: Toggle open/closed

Tutorial — switch opens a door

Section titled “Tutorial — switch opens a door”

1. Define a gameplay tag

Section titled “1. Define a gameplay tag”

Create a tag such as Message.OS.Door.Toggle under Project Settings → Gameplay Tags.

2. Broadcast from Terminal command

Section titled “2. Broadcast from Terminal command”

In your custom terminal command Blueprint:

Event Process Command
  → Get Global Message Subsystem
  → Broadcast Message (Filter Tag: Message.OS.Door.Toggle, Payload: optional door actor)
  → Continue Execution

3. Listen on the door actor

Section titled “3. Listen on the door actor”

On BP_Door Event BeginPlay:

Get Global Message Subsystem
  → Listen to Message (Filter Tag: Message.OS.Door.Toggle)
      Callback → Toggle Door Open/Closed
  → Remove Listener (self) after first use if one-shot

4. Test

Section titled “4. Test”

Play in editor, boot the OS, open Terminal, run your command. The door should react with no wire between Terminal Blueprint and door actor.

C++ broadcast

Section titled “C++ broadcast”
#include "GlobalMessageSubsystem.h"


void UCMD_ToggleDoor::OnProcessCommand()
{
    if (const UGlobalMessageSubsystem* MS = UGlobalMessageSubsystem::Get(*GetWorld()))
    {
        MS->BroadcastMessage(FGameplayTag::RequestGameplayTag("Message.OS.Door.Toggle"), nullptr);
    }
    ContinueExecution();
}

Build.cs:

PrivateDependencyModuleNames.AddRange(new string[] { "GlobalMessenger", "GameplayTags" });

C++ listen

Section titled “C++ listen”
UFUNCTION()
void ADoor::OnDoorMessage(UObject* Payload);


void ADoor::BeginPlay()
{
    Super::BeginPlay();
    if (UGlobalMessageSubsystem* MS = UGlobalMessageSubsystem::Get(*GetWorld()))
    {
        FGlobalMessageReceiveDelegate Delegate;
        Delegate.BindDynamic(this, &ADoor::OnDoorMessage);
        MS->ListenToMessage(this, DoorTag, Delegate);
    }
}

Viewport World integration

Section titled “Viewport World integration”

Global Messenger is how Viewport World spawns gameplay in a secondary world when a terminal command runs — see the preview video on the Global Messenger page.

Section titled “Related”