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How it works

UServerCoreSubsystem (GameInstanceSubsystem, server)   all logic, survives map changes
 ├─ UServerCoreStorage                                 persistence (default: JSON files)
 ├─ Command registry                                   built-in and custom commands
 └─ UServerCorePlayerComponent                         on every PlayerController, replicated
                                                       chat, commands, announcements, admin panel data
UServerCoreBlueprintLibrary                            helpers (player id, durations, permissions)
UServerCoreSettings                                    Project Settings → Plugins → Server Core

The subsystem​

UServerCoreSubsystem is a Game Instance Subsystem. There is one per server and it lives for the whole server session, across map changes. It tracks players, enforces bans and the whitelist at login, runs commands, schedules restarts and saves data.

Get it in Blueprint with Get Server Core, or in C++ with UServerCoreSubsystem::Get(this).

Callers​

Every moderation function takes an FServerCoreCaller: who is doing this?

CallerCreated withChecks
PlayerMake Caller (PlayerController)Permissions and group priority
SystemMake System Caller / server consoleNone, always allowed

Use a system caller for game logic, for example an anti-cheat ban, a vote kick or an automatic nightly restart. Use a player caller when an action comes from a player, so their permissions are respected.

warning

Callers are always built on the server. Never build a caller from data a client sent you. Clients send requests through the Player Component, and the server builds the caller from the connection.

Player ids​

Players are identified by their unique net id as a string (FUniqueNetIdRepl), for example a SteamID64 or an EOS ProductUserId. Get it with Get Player Id from a player controller.

Login enforcement​

Bans, IP bans and the whitelist are checked twice:

  1. PreLogin – the player is rejected before a player controller is spawned.
  2. PostLogin – as a fallback for game modes that override PreLogin, and for IP bans.

Saving​

Changes are saved automatically a fraction of a second after they happen, and everything is saved when the server shuts down. Files are written atomically, so a crash never leaves a half-written file.