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Documentation Index

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The MMOClient1 project is an Unreal Engine 5.4 game client built around a strict separation of concerns. HTTP-based authentication flows are isolated in UAuthClientSubsystem, while real-time gameplay communication over TCP and UDP lives in UGameClientSubsystem. Player controllers, UI widgets, character actors, and supporting subsystems each own a clearly bounded slice of responsibility, making the codebase straightforward to extend without cross-contaminating the auth layer and the gameplay layer.

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Module structure

The MMOClient1 module is configured in MMOClient1.Build.cs. Key aspects of the build setup include:
  • Engine modules: Core, CoreUObject, Engine, InputCore
  • UI modules: UMG, Slate, SlateCore
  • Networking modules: Sockets, Networking, HTTP
  • Serialization modules: Json, JsonUtilities
  • Additional modules: Niagara (VFX), MoviePlayer (loading screens), WebBrowserWidget (embedded HTML login page)
  • Third-party: libprotobuf and abseil_dll are linked from a vcpkg installation at C:\vcpkg\installed\x64-windows and staged alongside the executable at runtime. The PROTOBUF_USE_DLLS=1 definition enables DLL-mode protobuf. Exception handling is enabled via bEnableExceptions = true.
PublicDependencyModuleNames.AddRange(new string[]
{
    "Core", "CoreUObject", "Engine", "InputCore",
    "Niagara", "Slate", "SlateCore", "MoviePlayer",
    "Sockets", "Networking", "UMG", "WebBrowserWidget",
    "HTTP", "Json", "JsonUtilities"
});
The WebUI/... directory is staged as NonUFS so the standalone HTML login page ships with the packaged build.

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Subsystem split

The client’s network layer is divided into two UGameInstanceSubsystem classes, both accessible from any game code via GetGameInstance()->GetSubsystem<T>().
SubsystemResponsibility
UAuthClientSubsystemHTTP login, register, server list, server select, token storage
UGameClientSubsystemTCP game server connection, UDP movement channel, all gameplay packet send/receive
This mirrors the server-side split: the ASP.NET Core AuthServer owns all account/token logic, and the IOCP GameServer owns only post-authentication gameplay. The client follows the same boundary — AuthClientSubsystem never touches a game socket, and GameClientSubsystem never makes an HTTP call.

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Key classes

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ALoginPlayerController

A APlayerController subclass that drives the pre-game login flow. It creates and owns the ULoginWidget, binds to UAuthClientSubsystem’s OnSelectServerResult delegate, and — once a server is selected — calls UGameClientSubsystem::ConnectAndEnterGame with the enter token and character ID returned by the auth server. After the game enters successfully, ALoginPlayerController opens the gameplay level.

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AMCPlayerController

The in-game player controller. It owns the per-frame move-input loop, the combo-attack state machine, and all server-driven correction logic. It reads UGameClientSubsystem’s latest server location each tick and smoothly interpolates the controlled pawn toward the server-authoritative position. It also manages the UChatWidget, UInventoryWidget, and UGameExitMenuWidget UMG overlays, routing input to whichever panel is currently open.

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AMonsterCharacter

An ACharacter subclass that represents a server-spawned monster entity in the game world. It carries a UHealthComponent and a world-space UWidgetComponent for the health bar. On each server move notify, it interpolates toward the server target location using configurable LocationInterpSpeed and hard-snap thresholds. It also plays melee and ranged attack montages driven by server attack notifications, and Niagara tracer and muzzle-flash effects for ranged shots.

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UHealthComponent

A UActorComponent that tracks CurrentHp and MaxHp for any actor (player characters, monsters). It exposes InitializeHealth, ApplyServerHealth, and GetHealthRatio(), and broadcasts the OnHealthChanged dynamic multicast delegate whenever HP changes — used by AMonsterCharacter to refresh the health bar widget.

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UInventorySubsystem

A UGameInstanceSubsystem that holds the client-side inventory state received from the server. It stores the current Revision, Capacity, and a flat TArray<FInventoryItemState> of items (each with ItemInstanceId, TemplateId, Quantity, SlotIndex, Durability). UGameClientSubsystem calls ApplySnapshot when an S_InventorySnapshot or S_InventoryOperationResult packet arrives, which then broadcasts OnInventorySnapshotChanged for the UI to refresh.

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UItemRegistrySubsystem

A UGameInstanceSubsystem that loads all UItemDataAsset definitions via the Asset Manager at startup, building a TMap<int32, UItemDataAsset*> keyed by TemplateId. UI code calls FindItem(TemplateId) to retrieve display names and icons. UI-bundle soft references are streamed in on demand via RequestUiAssets(TemplateId), avoiding loading every icon into memory upfront.

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UItemDataAsset

A UPrimaryDataAsset subclass representing a single item template. Fields include:
  • TemplateId — matches the template_id used in inventory packets
  • DisplayName and Description — localized FText values shown in the inventory UI
  • Icon — TSoftObjectPtr<UTexture2D> loaded in the UI bundle
  • WorldStaticMesh / WorldSkeletalMesh — soft references for world-dropped item visuals

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UI widgets

LoginWidget

Hosts an embedded UWebBrowser that loads the HTML/JS login page. Handles unreal:// scheme URL callbacks from the page’s JavaScript to trigger UAuthClientSubsystem register and login calls. Also manages the post-login server list panel and ULoginServerEntryWidget rows.

GameMainWidget

The primary HUD overlay displayed during gameplay. Embeds the UChatWidget and owns a UProgressBar plus UTextBlock for the player’s health display. Calls SetPlayerHealth to update the bar when UGameClientSubsystem broadcasts an HP change.

ChatWidget

Displays a scrollable UScrollBox chat log and a text-input field. Opens on Enter, closes on commit or Escape. Binds to UGameClientSubsystem::OnChatMessageReceived and calls SendChatMessage on submit. Supports up to MaxVisibleMessages (default 100) lines.

InventoryWidget

Programmatically builds a UUniformGridPanel of UInventorySlotWidget cells at construction time. Refreshes slot visuals when UInventorySubsystem::OnInventorySnapshotChanged fires. Routes left-click and right-click slot input to UGameClientSubsystem::SendInventoryMove or SendInventoryUse.

InventorySlotWidget

A single inventory cell. Displays a UImage icon, a UTextBlock for quantity, and a border that highlights selection state and pending-operation state. Owned and refreshed by UInventoryWidget.

MonsterHealthBarWidget

World-space UMG widget attached to AMonsterCharacter via a UWidgetComponent offset above the monster’s head. Refreshed by AMonsterCharacter::RefreshHealthWidget whenever OnHealthChanged fires.

MCLoadingScreen

A movie-player loading screen widget displayed during level transitions (login level → gameplay level). Managed by the MoviePlayer module to overlay during seamless travel.

LoginServerEntryWidget

A single row in the server list panel inside ULoginWidget. Displays server name, current/max users, and maintenance status. Calls ULoginWidget::SelectServer when clicked.

GameExitMenuWidget

An escape-menu overlay managed by AMCPlayerController. Provides Quit Game and Return to Login actions. The controller calls SetExitMenuOpen(true/false) to show or hide it.

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WebUI login page

MMOClient1/WebUI/Login/login.html is a standalone HTML5 page served to the UWebBrowser widget inside ULoginWidget. It presents two views — a Login view and a Register view — and communicates results back to Unreal by setting window.location.hash to a uegame:// scheme URL (e.g. uegame://login?email=…&password=…&requestId=…). ULoginWidget watches for URL changes and parses the scheme to call the appropriate UAuthClientSubsystem method. The JavaScript exposes two callback entry points that Unreal can call via UWebBrowser::ExecuteJavascript:
  • setLoginResult(success, message) — re-enables the login button and shows a coloured status message
  • setRegisterResult(success, message) — does the same for the registration form
The page is staged as NonUFS so it is available in packaged builds without being cooked into the asset graph.
This project requires Unreal Engine 5.4 ("EngineAssociation": "5.4" in MMOClient1.uproject). The AnimationWarping, PoseSearch, AnimationLocomotionLibrary, MotionWarping, and Chooser plugins are all enabled and are part of UE5.4’s animation feature set. Opening the project with a different engine version will produce plugin compatibility errors.

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