# CFNetServiceBrowserClientCallBack Defines a pointer to the callback function for a CFNetServiceBrowser. ``` typealias CFNetServiceBrowserClientCallBack = (CFNetServiceBrowser, CFOptionFlags, CFTypeRef?, UnsafeMutablePointer?, UnsafeMutableRawPointer?) -> Void ``` ## Parameters `browser` The CFNetServiceBrowser associated with this callback function. `flags` Flags conveying additional information. The `kCFNetServiceFlagIsDomain` bit is set if `domainOrService` contains a domain; if this bit is not set, `domainOrService` contains a CFNetService instance. For additional bit values, see `CFNetServiceBrowserClientCallBack Bit Flags`. `domainOrService` A string containing a domain name if this callback function is being called as a result of calling [`CFNetServiceBrowserSearchForDomains(_:_:_:)`](/documentation/CFNetwork/CFNetServiceBrowserSearchForDomains(_:_:_:)), or a CFNetService instance if this callback function is being called as a result calling [`CFNetServiceBrowserSearchForServices(_:_:_:_:)`](/documentation/CFNetwork/CFNetServiceBrowserSearchForServices(_:_:_:_:)). `error` A pointer to a structure whose `error` field may contain an error code. `info` User-defined context information. The value of `info` is the same as the value of the `info` field of the [`CFNetServiceClientContext`](/documentation/CFNetwork/CFNetServiceClientContext) structure that was provided when [`CFNetServiceBrowserCreate(_:_:_:)`](/documentation/CFNetwork/CFNetServiceBrowserCreate(_:_:_:)) was called to create the CFNetServiceBrowser associated with this callback function. ## Discussion If you name your callback `MyNetServiceBrowserClientCallBack`, you would declare it like this: ### Discussion The callback function for a CFNetServiceBrowser is called one or more times when domains or services are found as the result of calling [`CFNetServiceBrowserSearchForDomains(_:_:_:)`](/documentation/CFNetwork/CFNetServiceBrowserSearchForDomains(_:_:_:)) and [`CFNetServiceBrowserSearchForServices(_:_:_:_:)`](/documentation/CFNetwork/CFNetServiceBrowserSearchForServices(_:_:_:_:)). --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)