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AP Event Bus
A server-authoritative, replicated event messaging system for Unreal Engine 5. Publish named events from anywhere. Listen from anywhere. No direct references required.
UE 5.7+ Multiplayer Ready No GAS Required 100% Blueprint Free
Quick Start API Reference Discord
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What Is It?
AP Event Bus is a pub/sub event messaging system for UE5 multiplayer. Any actor publishes a named event — identified by a Gameplay Tag — onto a bus. Any actor listens for events by tag. Publishers and listeners have no direct references to each other.
One PublishEvent node works from anywhere — clients, server, anywhere. Routing is handled automatically.
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Core Features
Any actor publishes events onto the bus. Any actor listens by tag. No direct actor references required between publishers and subscribers — fully decoupled event-driven architecture.
- All — server fires + NetMulticast to all connected clients
- OwnerOnly — server fires + Client RPC to the owning connection only
- ServerOnly — server fires locally, zero client cost
- LocalOnly — fires on the calling machine only, zero network cost — ideal for UI-only events
Call PublishEvent from a client, the server, or anywhere — one node handles all routing automatically. No authority checks, no separate RPC nodes, no different functions for different network roles.
Register events as persistent so their last payload is cached server-side. Late-joining clients automatically receive all cached events on connect — no manual state sync required.
- OnEventReceived — catch-all, fires for every event on the bus
- OnListenedEventReceived — filtered, fires only for tags you register via
ListenForEvent
Use both simultaneously on the same component.
WasEventFired, GetLastPayload, GetAllCachedEventTags — query persistent event state directly without waiting for a delegate.
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Start Here
Read the Quick Start Guide — global bus setup, publishing, listening, and late-join cache in minutes.
Browse the API Reference — every class, function, delegate, enum, and struct documented.
See the Changelog — version history and roadmap.
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What's Included
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Recommended Setup
Place one UAP_EventBusComponent on your GameState for a project-wide global bus accessible from any actor at any time. Alternatively place the component on any individual actor for a scoped per-actor bus.
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Technical Specs
AfterPrime Systems — Building the Gameplay Foundation