Making network request from iOS App Extension returns error: "A server with the specified hostname could not be found"

Question

I'm trying to download a language translation model from Google MLKit. I can download the model successfully on the main iOS app, but when I try to download it on the keyboard extension app, I receive an error: "A server with the specified hostname could not be found."

testKeyboard[43687:3987699] [] networkd_settings_read_from_file Sandbox is preventing this process from reading networkd settings file at "/Library/Preferences/com.apple.networkd.plist", please add an exception.
testKeyboard[43542:3979636] [discovery] [d 6BF0C0BD-3B78-43CD-A23F-26023D59A4F3] <PKHost:0x283acc400> Failed discovery: Error Domain=PlugInKit Code=4 "Connection invalid" UserInfo={NSLocalizedDescription=Connection invalid}.
testKeyboard[43542:3979636] [xpc] XPC error sending request to pkd: Connection invalid
testKeyboard[43542:3979662] [] nw_resolver_can_use_dns_xpc_block_invoke Sandbox does not allow access to com.apple.dnssd.service
testKeyboard[43542:3979662] dnssd_clientstub ConnectToServer: connect() failed path:/var/run/mDNSResponder Socket:9 Err:-1 Errno:1 Operation not permitted
testKeyboard[43542:3979662] [connection] nw_resolver_create_dns_service_locked [C1] DNSServiceCreateDelegateConnection failed: ServiceNotRunning(-65563)
testKeyboard[43542:3979662] Task <38FA4936-22C4-4E80-BECC-1D592945BE52>.<1> HTTP load failed, 0/0 bytes (error code: -1003 [10:-72000])
testKeyboard[43542:3979662] Task <38FA4936-22C4-4E80-BECC-1D592945BE52>.<1> finished with error [-1003] Error Domain=NSURLErrorDomain Code=-1003 "A server with the specified hostname could not be found." UserInfo={_kCFStreamErrorCodeKey=-72000, NSUnderlyingError=0x2821c14a0 {Error Domain=kCFErrorDomainCFNetwork Code=-1003 "(null)" UserInfo={_kCFStreamErrorCodeKey=-72000, _kCFStreamErrorDomainKey=10}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDownloadTask <38FA4936-22C4-4E80-BECC-1D592945BE52>.<1>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalDownloadTask <38FA4936-22C4-4E80-BECC-1D592945BE52>.<1>"
), NSLocalizedDescription=A server with the specified hostname could not be found., NSErrorFailingURLStringKey=https://redirector.gvt1.com/edgedl/translate/offline/v5/high/r24/en_es.zip, NSErrorFailingURLKey=https://redirector.gvt1.com/edgedl/translate/offline/v5/high/r24/en_es.zip, _kCFStreamErrorDomainKey=10}
error downloading Optional(Error Domain=com.google.mlkit Code=2 "Failed to download the model from the server." UserInfo={NSLocalizedDescription=Failed to download the model from the server.})

I'm using the same code to download the model according to Google's "Translate Text with MLKit on iOS" documentation in the KeyboardViewController's viewDidLoad() function:

        let options = TranslatorOptions(sourceLanguage: .english, targetLanguage: .spanish)
        self.translator = Translator.translator(options: options)
        let conditions = ModelDownloadConditions(allowsCellularAccess: true, allowsBackgroundDownloading: true )
        self.translator!.downloadModelIfNeeded(with: conditions) { error in
            guard error == nil else {
                print("error downloading", error)
                return
            }
            print("Model downloaded successfully")
        }

My Info.plist settings are such:

1. "RequestsOpenAccess" as 1
2. "App Transport Security Settings" > "Allow Arbitrary Loads" as YES

I don't understand what is going on here. Why am I able to download the ML Kit language model on the main app, but not on the keyboard extension? Any help appreciated.

Answer 1

The issue is with your project's Sandbox settings. Go to your project page / Signing & Capabilities / App Sandbox (Xcode 13.2) and then enable Outgoing Connections (Client) which will allow your app to make http calls.