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  "title" : "AccessoryTransportSession.EventHandler"
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# AccessoryTransportSession.EventHandler

A protocol that defines methods for handling transport session events.

```
protocol EventHandler
```

## Overview

Implement this protocol to respond to data events and session invalidation in your transport extension.

## Topics

### Handling data events

[`func dataEventHandler(event: AccessoryTransportSession.DataEvent)`](/documentation/AccessoryTransportExtension/AccessoryTransportSession/EventHandler/dataEventHandler(event:))

Handles events that address incoming data destined for the accessory.

[`func messageReceived(TransportMessage, completion: (AccessoryMessage.Result) -> Void)`](/documentation/AccessoryTransportExtension/AccessoryTransportSession/EventHandler/messageReceived(_:completion:))

Handles incoming messages for transmission to the accessory.

### Handling the session life cycle

[`func invalidationHandler(error: AccessoryTransportSession.Error?)`](/documentation/AccessoryTransportExtension/AccessoryTransportSession/EventHandler/invalidationHandler(error:))

Handles session invalidation.

### Instance Methods

[`func sessionInvalidated(error: AccessoryTransportSession.Error?)`](/documentation/AccessoryTransportExtension/AccessoryTransportSession/EventHandler/sessionInvalidated(error:))

Handles session invalidation.

---

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