Client Callbacks

Connection Callbacks

Every callback on this page is a public Broadcaster member of RealtimeClient, except for the custom-event subscriptions listed under Event Subscriptions. Subscribe with client.OnXxx.Subscribe(handler), which returns a Subscription; see Callbacks and Subscriptions for the lifetime rules and RAII helpers.

Over the C API there is nothing to subscribe to: every callback below is pre-subscribed and delivered as a numbered event on the client's event queue. Broadcaster Events maps each callback to its event number and to the fields its parameters arrive in.

Callback	Fires When	Manual Page
`OnDisconnected(DisconnectCause cause)`	The connection ends, requested or not; `cause` carries the reason.	Errors and Disconnects
`OnError(ErrorCode code, StringViewType message)`	An asynchronous error occurs outside a pending operation.	Errors and Disconnects
`OnCustomAuthStep(const std::unordered_map<StringType, StringType>& data)`	A custom authentication provider requests another authentication step.	Authentication

Room and Player Callbacks

Callback	Fires When	Manual Page
`OnRoomJoined()`	The local client enters a room, by creating or joining it.	Rooms and Players
`OnRoomLeft()`	The local client leaves the current room.	Rooms and Players
`OnPlayerJoined(const PlayerView& player)`	A remote player joins the current room.	Rooms and Players
`OnPlayerLeft(int playerNumber, bool isInactive)`	A player leaves the current room; `isInactive` is `true` when the player may still rejoin.	Rooms and Players
`OnMasterClientChanged(int newId, int oldId)`	Mastership moves from player `oldId` to player `newId`.	Rooms and Players

Property Callbacks

Callback	Fires When	Manual Page
`OnRoomPropertiesChanged(const RealtimeMap& changes)`	The room's custom properties change; the map contains only the changed keys.	Custom Properties
`OnPlayerPropertiesChanged(int playerNumber, const RealtimeMap& changes)`	A player's custom properties change.	Custom Properties
`OnPropertiesChangeFailed()`	The server rejects a property update, for example a failed compare-and-swap.	Custom Properties

Event Subscriptions

Custom events are not a Broadcaster member. They are registered on RealtimeClient itself, with an event-code filter baked into the subscription; every overload returns the same Subscription type as Subscribe() does. The payload form is deduced from the callback: std::span<const uint8_t> delivers raw bytes, const RealtimeValue& delivers the decoded payload.

Subscription	Delivers	Manual Page
`SubscribeEvent(callback)`	Every event code, `0` through `255`.	Custom Events
`SubscribeEvent(uint8_t eventCode, callback)`	Only `eventCode`.	Custom Events
`SubscribeEvent(uint8_t firstEventCode, uint8_t lastEventCode, callback)`	The inclusive code range.	Custom Events
`SubscribeEvent<Payload>(...)`	The same three overloads with the payload form named explicitly, `std::span<const uint8_t>` or `const RealtimeValue&` (plain `RealtimeValue` is accepted as shorthand).	Custom Events
`SubscribeEvent<T>(uint8_t eventCode, callback)`	`eventCode` only, decoded into a trivially-copyable `T`; the callback takes `(int senderId, const T& value)`.	Custom Events

The callback signature of the untyped overloads is (uint8_t eventCode, int senderId, PayloadType payload). A byte-span payload points into a decode buffer owned by the subscription and is only valid during the call.

Direct Messaging Callbacks

Callback	Fires When	Manual Page
`OnDirectMessage(int senderId, std::span<const uint8_t> data, bool isRelay)`	A direct message arrives; `isRelay` is `true` when it traveled through the server instead of peer-to-peer.	Direct Messaging
`OnDirectConnectionEstablished(int remotePlayerId)`	A peer-to-peer connection to a remote player is established.	Direct Messaging
`OnDirectConnectionFailed(int remotePlayerId)`	A peer-to-peer connection attempt to a remote player fails.	Direct Messaging

Lobby Callbacks

Callback	Fires When	Manual Page
`OnRoomListUpdated(const std::vector<RoomListing>& rooms)`	The room list of the joined lobby changes.	Lobbies and Matchmaking
`OnLobbyStats(const std::vector<LobbyStats>& stats)`	Lobby statistics arrive, requested via `GetLobbyStats()` or pushed when `AutoLobbyStats` is enabled.	Lobbies and Matchmaking

Advanced Callbacks

Callback	Fires When	Manual Page
`OnWarning(int warningCode)`	The SDK reports a non-fatal warning.	Errors and Disconnects
`OnAppStatsUpdated()`	The server pushes fresh application statistics; read them via `GetStats()`.	Statistics
`OnCacheSliceChanged(int cacheSliceIndex)`	The room's event cache slice index changes.	Event Caching
`OnCustomOperationResponse(uint8_t opCode, int errorCode, StringViewType errorString, const RealtimeMap& data)`	A custom server operation sent with `SendCustomOperation()` responds.	Configuration

Last updated on 20/08/2026

Connection Callbacks
Room and Player Callbacks
Property Callbacks
Event Subscriptions
Direct Messaging Callbacks
Lobby Callbacks
Advanced Callbacks