You have to add defaultLocalization to your Package.swift and it should work let package = Package( name: "YourName", defaultLocalization: "en", <--- platforms: [ .iOS(.v16) ], ...

iOS has a sandbox, but it’s not exactly the same sandbox as the App Sandbox on macOS. Notably, the iOS sandbox does not require an entitlement to access the network, which is why you’re not seeing the problem there. It makes sense. Why do you need to run an HTTP server in your UI test runner? For instance, in iOS, I use a simple HTTP localhost server with which I can mock responses and status codes for endpoints used in the app. This approach is useful if I want to run quick tests that simply navigate through the app to verify if screens and views are displayed as expected, based on the provided data. This way, I can avoid relying on scripts that set up my backend app or using non-native frameworks written in Python. pps As you’ve probably noticed, calling BSD Sockets from Swift is a royal pain. I have some helpers that I use for this; see Calling BSD Sockets from Swift. Note that these aren’t intended for production code, but are helpful in cases like this. I'm gonna check!