Messenger Subsystems

Two messenger systems let you wire the simulated OS to gameplay without tight coupling.

Choose the right bus

Subsystem	Scope	Identifiers	Best for
Global Messenger	Entire UWorld	Gameplay tags	Terminal → door, switch → level sequence
Device Messenger	One running device	FName events	Mail badge, battery UI, program ↔ program

flowchart TB
  subgraph global["Global Messenger — world scope"]
    direction LR
    Term["UOperatingSystemTerminalCommand"] --> GM["UGlobalMessageSubsystem"] --> Door["Level actor listener"]
  end
  subgraph device["Device Messenger — device scope"]
    direction LR
    Mail["BP_Prog_Mail"] --> DM["FOperatingSystemDeviceMessengerSystem"] --> Taskbar["UOperatingSystemTaskbarButton"]
  end

Tutorials

Tutorial	Focus
Using Global Messenger	Door toggle from terminal
Using Device Messenger	In-device program events

API

• UGlobalMessageSubsystem
• FOperatingSystemDeviceMessengerSystem
• UOperatingSystemStatics::FindMessengerFromOperatingSystem

sequenceDiagram
  participant T as UOperatingSystemTerminalCommand
  participant G as UGlobalMessageSubsystem
  participant A as Any world listener
  participant D as FOperatingSystemDeviceMessengerSystem
  participant P as UOperatingSystemBaseProgram
  Note over T,A: World scope
  T->>G: BroadcastMessage(gameplay tag)
  G->>A: ListenToMessage callback
  Note over D,P: Device scope only
  P->>D: Broadcast(FName event)
  D->>P: BeginListening callback

Demo

The standalone demo opens a roof door via Global Messenger with zero direct references between Terminal and actors.