> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xbox.com/llms.txt
> Use this file to discover all available pages before exploring further.

# XblRealTimeActivityAddResyncHandler

> Registers a handler that's called when the Real-Time Activity (RTA) service sends a resync message.

Registers a handler function to receive a notification that is sent when there is a resync message from the Real-Time Activity (RTA) service.

## Syntax

```cpp theme={null}
XblFunctionContext XblRealTimeActivityAddResyncHandler(  
         XblContextHandle xboxLiveContext,  
         XblRealTimeActivityResyncHandler* handler,  
         void* context  
)  
```

### Parameters

*xboxLiveContext*   \_In\_\
Type: [XblContextHandle](https://docs.xbox.com/reference/live/xsapi-c/types_c/handles/xblcontexthandle.md)

XBOX services context handle.

*handler*   \_In\_\
Type: [XblRealTimeActivityResyncHandler\*](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/functions/xblrealtimeactivityresynchandler.md)

The callback function that receives notifications.

*context*   \_In\_opt\_\
Type: void\*

Caller context that will be passed back to the handler function.

### Return value

Type: XblFunctionContext

A XblFunctionContext object that can be used to unregister the event handler. Pass it to [XblRealTimeActivityRemoveResyncHandler](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/functions/xblrealtimeactivityremoveresynchandler.md).

A successful registration returns a token greater than 0. If the function fails, it can return an HRESULT error code cast to `XblFunctionContext`, which is a negative value. Possible error codes include the following. This list isn't exhaustive.

| Return code | Description |
| - | - |
| E\_INVALIDARG | *xboxLiveContext* or *handler* is null. |
| E\_XBL\_NOT\_INITIALIZED | The XBOX services API (XSAPI) isn't initialized. Call [XblInitialize](https://docs.xbox.com/reference/live/xsapi-c/xbox_live_global_c/functions/xblinitialize.md) first. |

## Remarks

This message indicates that data may have been lost and to resync all data by calling corresponding REST API's. Wherever possible, XSAPI will automatically resync the subscription and invoke the corresponding handler. For multiplayer session changed subscriptions, titles must resync their own sessions.

## Requirements

**Header:** real\_time\_activity\_c.h

**Library:** Microsoft.Xbox.Services.142.C.lib or Microsoft.Xbox.Services.143.C.lib

## See also

[real\_time\_activity\_c](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/real_time_activity_c_members.md)


## Related topics

- [XblRealTimeActivitySubscriptionErrorHandler](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/functions/xblrealtimeactivitysubscriptionerrorhandler.md)
- [real_time_activity_c (contents)](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/real_time_activity_c_members.md)
- [Privacy and permissions overview](https://docs.xbox.com/services/xbox-services/fundamentals/identity/privacy/live-privacy-overview.md)
- [XblRealTimeActivityResyncHandler](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/functions/xblrealtimeactivityresynchandler.md)
- [XblRealTimeActivityRemoveResyncHandler](https://docs.xbox.com/reference/live/xsapi-c/real_time_activity_c/functions/xblrealtimeactivityremoveresynchandler.md)