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# FxPrincipalDelegate

A protocol that provides information about the host application that launched your XPC service.

```
protocol FxPrincipalDelegate
```

## Overview

When the host application first launches your XPC Service, your XPC calls +[`startServicePrincipal(with:)`](/documentation/professional_video_applications/FxPrincipal/startServicePrincipal(with:)) to get communication with the host application started. Passing in a delegate allows you to know which host application and version launched your XPC service.

## Topics

### Instance Method

[`func didEstablishConnection(withHost: String!, version: String!)`](/documentation/professional_video_applications/FxPrincipalDelegate/didEstablishConnection(withHost:version:))

Notifies your XPC service that a connection was established with the host.


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