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Explore the networking protocols and technologies used by the device to connect to Wi-Fi networks, Bluetooth devices, and cellular data services.

Networking Documentation

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5G Network Slicing and NetworkExtension
Hello, I am writing a NetworkExtension VPN using custom protocol and our client would like to able to use 5G network slice on the VPN, is this possible at all? From Apple's documentation, I found the following statement: If both network slicing and VPN are configured for an app or device, the VPN connection takes precedence over the network slice, rendering the network slice unused. Is it possible to assign a network slice on a NetworkExtension-based VPN and let the VPN traffic uses the assign network slice? Many thanks
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621
Dec ’25
DTLS Handshake Fails When App Is in Background – Is This an iOS Limitation?
Hello, We are facing an issue with performing a DTLS handshake when our iOS application is in the background. Our app (Vocera Collaboration Suite – VCS) uses secure DTLS-encrypted communication for incoming VoIP calls. Problem Summary: When the app is in the background and a VoIP PushKit notification arrives, we attempt to establish a DTLS handshake over our existing socket. However, the handshake consistently fails unless the app is already in the foreground. Once the app is foregrounded, the same DTLS handshake logic succeeds immediately. Key Questions: Is performing a DTLS handshake while the app is in the background technically supported by iOS? Or is this an OS-level limitation by design? If not supported, what is the Apple-recommended alternative to establish secure DTLS communication for VoIP flows without bringing the app to the foreground? Any guidance or clarification from Apple engineers or anyone who has solved a similar problem would be greatly appreciated. Thank you.
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2w
Accessory Setup Kit (BLE) not showing multiple options nor the advertising name
I'm developing an application using the accessory setup kit (BLE) on iOS 18+. An important aspect of the connection process is being able to find and choose the correct device. I noticed on iOS 18.2 that I was able to both scroll through the discovered accessories as well as view the advertised name. However, after upgrading to 18.7.2, only a single device is viewable and the advertised name is no longer available. Is there a trigger for this feature that I need to enable or was this "multiple discovery" feature removed? If so, why?
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202
Oct ’25
Safari block the access to some port of an IP on the whole system
Hi, Since iOS 26 (and any other apple system with a 26 version) there is a very weird behavior in the whole apple ecosystem (iOS, iPadOS, macOS and visionOS). I'm self-hosting a web project called mempool (https://github.com/Retropex/mempool). This project is entirely self-hosted on my own infrastructure, so I have advanced control to be sure it's just not an anti-DDoS feature that makes the bug happen. So the bug is once I visit my website, for example this page (https://mempool.guide/tx/d86192252a6631831e55f814aea901e65407b6dbda77e1abdea8ec27861e9682) the OS will lose the ability to connect to the underlying IP of the domain (mempool.guide) but the issue seems to affect only the HTTPS/HTTP port (443/80). The issue is system wide, not only is Safari. For exemple I have another domain that resolve to the same IP (haf.ovh) and if this link above trigger the bug then I will also lose the ability to connect to https://haf.ovh A temporary fix that I have is that if I turn off wifi/cellular then I turn it on again I can connect again to my server again until the bug is triggered again. I have done test with tcpdump on my server and the connection isn't making it to my server that's why I think it's an OS issue, especially given the fix above. This issue can be reproduced on any apple device out of the box with a system with >v26. All device (Mac, iPad, iPhone, vision) with version pre-26 are completely unaffected by the bug and can freely explore the website without loosing the connection macOS is less affected by this bug, it can be random with it. With iOS/iPadOS it's systematic. Another thing to note is that the same URL on firefox/chrome for iOS doesn't trigger the bug. Let me know if anyone has an idea on what's going on. Thanks, Léo.
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174
Oct ’25
Apple-Hosted Background Assets question
I have a Vision Pro app, which I intend to use Apple-Hosted Background Assets for some of my videos after watching: https://developer.apple.com/videos/play/wwdc2025/325 I added a Apple-Hosted, Managed extension. New Target -> Background Download -> Apple-Hosted, Managed After creating an Archive, I tried uploading it to TestFlight, it complains about a DTPlatformName error in my Info.plist. So I added the following : <key>DTPlatformName</key> <string>xros</string> With which, I managed to upload the app with the extension to TestFlight. However, when I tried installing the app on TestFlight to Vision Pro, it gives me an error that says the app cannot be verified. Any help or pointers is greatly appreciated. Info.plist Entitlements
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212
Oct ’25
Completion handler blocks are not supported in background sessions
When I try to implement the new Background Task options in the same way as they show in the WWDC video (on watchOS) likes this: let config = URLSessionConfiguration.background(withIdentifier: "SESSION_ID") config.sessionSendsLaunchEvents = true let session = URLSession(configuration: config) let response = await withTaskCancellationHandler {       try? await session.data(for: request) } onCancel: {       let task = session.downloadTask(with: request))       task.resume() } I'm receiving the following error: Terminating app due to uncaught exception 'NSGenericException', reason: 'Completion handler blocks are not supported in background sessions. Use a delegate instead.' Did I forget something?
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2.7k
Apr ’25
VPN Split DNS behaviour
I encountered an undesired DNS behaviour when using L2TP/ipsec VPN. I have DHCP configured Wi-Fi connection, which send dns servers and search domain (192.168.0.10, lan) VPN sends its own DNS server (10.0.0.2), search domain (intranet) is added manually in VPN DNS config settings. I expect, when VPN is connected, to be still able to resolve local names, i.e some-host.lan. However, they become unresolvable. quick check shows that the remote dns server is used to resolve local names. shilishper@mac ~ % host -v some-host.lan Trying "some-host.lan" Host some-host.lan not found: 3(NXDOMAIN) Received 106 bytes from 10.0.0.2#53 in 16 ms Received 106 bytes from 10.0.0.2#53 in 16 ms Actually, all dns queries are going to the remote server. I would expect that only queries for the configured domain (intranet) should go to that server. I played with the service order, but it didn't change anything. Is anything can be done about this, programmatically? PS new to macOS, but have extensive linux knowledge
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163
Sep ’25
URL Filter not blocking specified keywords
I have been playing around with the new URL Filtering API. I have successfully installed and configured the sample code, Installed the example app to my iPhone, and am also running the PIR server locally on my Mac. In my input.txtpb file, I simply have 2 endpoints: rows: [{ keyword: "instagram.com", value: "1" }, { keyword: "youtube.com/shorts", value: "1" }] Neither of these are blocked when I attempt to load them from either a browser, or their dedicated apps. Are there any debugging tips I should know about? Additionally, I have also noticed a few times I have left the filter running on my phone, after leaving my LAN (where the PIR server is running), suddenly throughout the day I'm having random, completely unrelated endpoints blocked on my phone. I thought this API was never supposed to produce false positives (without calling back to the PIR server for confirmation).
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164
Sep ’25
SSL certificate failure
This problem doesn’t appear to relate to the app as everything worked when using http (although an https setup issue may still be the problem). The problem appears to relate to the SSL server certificate on the Ubuntu server and the fact that apple does not accept that it is secure. However I have no problem with the equivalent Android app or web browser connections to the same rest API web services. There are numerous posts on these problems on Apple and other Forums, but none have helped me successfully address the issue. I ran an SSL server test on https://www.ssllabs.com/ssltest/ which gives ratings for SSL sites. The test gave an A rating although a number of minor issues were shown that may be crucial to the iOS failure. Some Sectigo certificates said self signed, which I couldn't understand. Error message from XCode log attached 2025-09-10 10:28:01.725091+0100 locateandclock[2291:1585213] ATS failed system trust 2025-09-10 10:28:01.725192+0100 locateandclock[2291:1585213] Connection 1: system TLS Trust evaluation failed(-9802) 2025-09-10 10:28:01.725291+0100 locateandclock[2291:1585213] Connection 1: TLS Trust encountered error 3:-9802 2025-09-10 10:28:01.725352+0100 locateandclock[2291:1585213] Connection 1: encountered error(3:-9802) 2025-09-10 10:28:01.726727+0100 locateandclock[2291:1585213] Task <4E41098F-6B71-4FB8-8753-78DD32961812>.<1> HTTP load failed, 0/0 bytes (error code: -1200 [3:-9802]) 2025-09-10 10:28:01.736504+0100 locateandclock[2291:1585213] Task <4E41098F-6B71-4FB8-8753-78DD32961812>.<1> finished with error [-1200] Error Domain=NSURLErrorDomain Code=-1200 "An SSL error has occurred and a secure connection to the server cannot be made." UserInfo={NSLocalizedRecoverySuggestion=Would you like to connect to the server anyway?, _kCFStreamErrorDomainKey=3, NSErrorPeerCertificateChainKey=( "<cert(0x10681be00) s: *.xxxxxxxxxxx.co.uk i: Sectigo Public Server Authentication CA DV R36>", "<cert(0x10681c800) s: Sectigo Public Server Authentication CA DV R36 i: Sectigo Public Server Authentication Root R46>", "<cert(0x10681d200) s: Sectigo Public Server Authentication Root R46 i: Sectigo Public Server Authentication Root R46>" ), NSErrorClientCertificateStateKey=0, NSErrorFailingURLKey=https://xxxxxxxxxxxx.co.uk/insertclocking, NSErrorFailingURLStringKey=https://xxxxxxxxxxxx.co.uk/insertclocking, NSUnderlyingError=0x282361650 {Error Domain=kCFErrorDomainCFNetwork Code=-1200 "(null)" UserInfo={_kCFStreamPropertySSLClientCertificateState=0, kCFStreamPropertySSLPeerTrust=<SecTrustRef: 0x281cf4460>, _kCFNetworkCFStreamSSLErrorOriginalValue=-9802, _kCFStreamErrorDomainKey=3, _kCFStreamErrorCodeKey=-9802, kCFStreamPropertySSLPeerCertificates=( "<cert(0x10681be00) s: *.xxxxxxxxxxxxxco.uk i: Sectigo Public Server Authentication CA DV R36>", "<cert(0x10681c800) s: Sectigo Public Server Authentication CA DV R36 i: Sectigo Public Server Authentication Root R46>", "<cert(0x10681d200) s: Sectigo Public Server Authentication Root R46 i: Sectigo Public Server Authentication Root R46>" )}}, _NSURLErrorRelatedURLSessionTaskErrorKey=( "LocalDataTask <4E41098F-6B71-4FB8-8753-78DD32961812>.<1>" ), _kCFStreamErrorCodeKey=-9802, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <4E41098F-6B71-4FB8-8753-78DD32961812>.<1>, NSURLErrorFailingURLPeerTrustErrorKey=<SecTrustRef: 0x281cf4460>, NSLocalizedDescription=An SSL error has occurred and a secure connection to the server cannot be made.}
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299
Oct ’25
Network extension doesn't get the updated preferred language after changing phone language
We’ve noticed an issue where after running a network extension, if the phone’s language is changed the Locale.preferredLanguages array is not updated and still returns the old array. It only returns the updated array when the app is reinstalled or the phone is restarted. This is unlike the app itself where using the same Locale.preferredLanguages API immediately returns the updated array. We think this issue is also the cause of notifications that are sent by the network extension being in the previous language as long as the app isn’t reinstalled or the phone is restarted, despite our Localizable file having localised strings for the new language. Feedback ID: FB20086051 The feedback report includes a sample project with steps on how to reproduce the issue.
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207
Sep ’25
Missing flows for content filter on macOS 15 Sequoia
We use as content filter in our app to monitor flows, we gather data about the flow and block flows deemed suspicious. Our content filter is activated/deactivated by a UI app but the flows are reported via XPC to a separate daemon process for analysis. As of macOS 15, we are seeing cases where flows are missing or flows are not received at all by the content filter. The behaviour is not consistent, some devices seem to receive flows normally but others don't. It appears Intel devices are much less prone to showing the problem, whereas Arm devices routinely exhibit missing flows. On macOS 14 or earlier, there is no sign of missing flows. Testing on earlier beta versions of macOS 15 did not appear to show the problem, however I can't rule out if issue was present but it wasn't spotted. Experimenting with simple examples of using a content filter (e.g. QNE2FilterMac) does not appear to reproduce the issue. Questions, What has changed between macOS 14 and 15 that could be the cause of the lack of flows? Is our approach to using an app activated content filter reporting to a daemon connected via XPC unsupported?
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1.1k
Aug ’25
Local Push Connectivity - Unreliable Connection
Hi! My project has the Local Push Connectivity entitlement for a feature we have requiring us to send low-latency critical notifications over a local, private Wi-Fi network. We have our NEAppPushProvider creating a SSE connection using the Network framework with our hardware running a server. The server sends a keep-alive message every second. On an iPhone 16 with iOS 18+, the connection is reliable and remains stable for hours, regardless of whether the iOS app is in the foreground, background, or killed. One of our QA engineers has been testing on an iPhone 13 running iOS 16, and has notice shortly after locking the phone, specifically when not connected to power the device seems to turn off the Wi-Fi radio. So when the server sends a notification, it is not received. About 30s later, it seems to be back on. This happens on regular intervals. When looking at our log data, the provider does seem to be getting stopped, then restarted shortly after. The reason code is NEProviderStopReasonNoNetworkAvailable, which further validates that the network is getting dropped by the device in regular intervals. My questions are: Were there possibly silent changes to the framework between iOS versions that could be the reason we're seeing inconsistent behavior? Is there a connection type we could use, instead of SSE, that would prevent the device from disconnecting and reconnecting to the Wi-Fi network? Is there an alternative approach to allow us to maintain a persistent network connection with the extension or app?
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308
Jul ’25
PacketTunnelProvider gets corrupted when app updated with connected Tunnel
We currently supporting proxy app with Tunnel.appEx and PacketTunnelProvider. Some users report about constant error "The VPN session failed because an internal error occurred." on VPN start (which fails rapidly). This error occur mostly after user updated app with active VPN. Rebooting device solves the problem and it doesnt come again, but it is still very frustrating. I can provide any required info about app setup to solve this issue if you need. Thanks
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199
Aug ’25
URL Filter - blocked web page behaviour
1) Blocked page UX When a URL is blocked, the browser typically shows a generic error like “"Safari cannot open the page because it couldn’t load any data,” with no indication that the page was blocked by a policy. Is there any plan to add an API that allows developers to present a custom “blocked” page or remediation action, similar to NEFilterControlProvider’s remediationMap? Even a minimal hook (custom HTML, deep link, or support URL) would make the experience clearer for users. 2) Cross‑app link‑opening behavior With a block rule in place, direct navigation in Safari is blocked as expected. However, tapping the same URL in a messaging app (e.g., WhatsApp) opens Safari - and the page loads, not blocked. Repro steps: Configure a URL Filter extension that blocks https://example.com. Case A: Open a browser and type the URL in the address bar → blocked (expected). Case B: Tap the same URL in WhatsApp (or another messenger) → a browser opens and the page loads (unexpected). iOS version - 26.0
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NWConnection: how to recover data connection after RF cellular data connection loss
iOS Development environment Xcode 16.4, macOS 15.6.1 (24G90) Run-time configuration: iOS 17.2+ Short Description After having successfully established an NWConnection (either as UDP or TCP), and subsequently receiving the error code: UDP Connection failed: 57 The operation couldn't be completed. (Network.NWError error 57 - Socket is not connected), available Interfaces: [enO] via NWConnection.stateUpdateHandler = { (newState) in ... } while newState == .failed the data connection does not restart by itself once cellular (RF) telephony coverage is established again. Detailed Description Context: my app has a continuous cellular data connection while in use. Either a UDP or a TCP connection is established depending on the user settings. The setup data connection works fine until the data connection gets disconnected by loss of connection to a available cellular phone base station. This disconnection simply occurs in very poor UMTS or GSM cellular phone coverage. This is totally normal behavior in bad reception areas like in mountains with signal loss. STEPS TO REPRODUCE Pre-condition App is running with active data connection. Action iPhone does loss the cellular data connection previously setup. Typically reported as network error code 57. Observed The programmed connection.stateUpdateHandler() is called in network connection state '.failed' (OK). The self-programmed data re-connection includes: a call to self.connection.cancel() a call to self.setupUDPConnection() or self.setupConnection() depending on the user settings to re-establish an operative data connection. However, the iPhone's UMTS/GSM network data (re-)connection state is not properly identified/notified via NWConnection API. There's no further network state notification by means of NWConnection even though the iPhone has recovered a cellular data network. Expected The iPhone or any other means automatically reconnects the interrupted data connection on its own. The connection.stateUpdateHandler() is called at time of the device's networking data connection (RF) recovering, subsequently to a connection state failed with error code 57, as the RF module is continuously (independently from the app) for available telephony networks. QUESTION How to systematically/properly detect a cellular phone data network reconnection readiness in order to causally reinitialize the NWConnection data connection available used in app. Relevant code extract Setup UDP connection (or similarly setup a TCP connection) func setupUDPConnection() { let udp = NWProtocolUDP.Options.init() udp.preferNoChecksum = false let params = NWParameters.init(dtls: nil, udp: udp) params.serviceClass = .responsiveData // service type for medium-delay tolerant, elastic and inelastic flow, bursty, and long-lived connections connection = NWConnection(host: NWEndpoint.Host.name(AppConstant.Web.urlWebSafeSky, nil), port: NWEndpoint.Port(rawValue: AppConstant.Web.urlWebSafeSkyPort)!, using: params) connection.stateUpdateHandler = { (newState) in switch (newState) { case .ready: //print("UDP Socket State: Ready") self.receiveUDPConnection(). // data reception works fine until network loss break case .setup: //print("UDP Socket State: Setup") break case .cancelled: //print("UDP Socket State: Cancelled") break case .preparing: //print("UDP Socket State: Preparing") break case .waiting(let error): Logger.logMessage(message: "UDP Connection waiting: "+error.errorCode.description+" \(error.localizedDescription), available Interfaces: \(self.connection.currentPath!.availableInterfaces.description)", LoggerLevels.Error) break case .failed(let error): Logger.logMessage(message: "UDP Connection failed: "+error.errorCode.description+" \(error.localizedDescription), available Interfaces: \(self.connection.currentPath!.availableInterfaces.description)", LoggerLevels.Error) // data connection retry (expecting network transport layer to be available) self.reConnectionServer() break default: //print("UDP Socket State: Waiting or Failed") break } self.handleStateChange() } connection.start(queue: queue) } Handling of network data connection loss private func reConnectionServer() { self.connection.cancel() // Re Init Connection - Give a little time to network recovery let delayInSec = 30.0. // expecting actually a notification for network data connection availability, instead of a time-triggered retry self.queue.asyncAfter(deadline: .now() + delayInSec) { switch NetworkConnectionType { case 1: self.setupUDPConnection() // UDP break case 2: self.setupConnection() // TCP break default: break } } } Does it necessarily require the use of CoreTelephony class CTTelephonyNetworkInfo or class CTCellularData to get notifications of changes to the user’s cellular service provider?
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358
Sep ’25
macOS 15.6 network failure with VPNs?
I filed FB19631435 about this just now. Basically: starting with 15.6, we've had reports (internally and outternally) that after some period of time, networking fails so badly that it can't even acquire a DHCP lease, and the system needs to be rebooted to fix this. The systems in question all have at least 2 VPN applications installed; ours is a transparent proxy provider, and the affected system also had Crowdstrike's Falcon installed. A customer system reported seemingly identical failures on their systems; they don't have Crowdstrike, but they do have Cyberhaven's. Has anyone else seen somethng like this? Since it seems to involve three different networking extensions, I'm assuming it's due to an interaction between them, not a bug in any individual one. But what do I know? 😄
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474
Jan ’26
peer-to-peer networking for iOS, iPadOS, watchOS, tvOS
Our product (rockhawk.ca) uses the Multipeer Connectivity framework for peer-to-peer communication between multiple iOS/iPadOS devices. My understanding is that MC framework communicates via three methods: 1) infrastructure wifi (i.e. multiple iOS/iPadOS devices are connected to the same wifi network), 2) peer-to-peer wifi, or 3) Bluetooth. In my experience, I don't believe I've seen MC use Bluetooth. With wifi turned off on the devices, and Bluetooth turned on, no connection is established. With wifi on and Bluetooth off, MC works and I presume either infrastructure wifi (if available) or peer-to-peer wifi are used. I'm trying to overcome two issues: Over time (since iOS 9.x), the radio transmit strength for MC over peer-to-peer wifi has decreased to the point that range is unacceptable for our use case. We need at least 150 feet range. We would like to extend this support to watchOS and the MC framework is not available. Regarding #1, I'd like to confirm that if infrastructure wifi is available, MC uses it. If infrastructure wifi is not available, MC uses peer-to-peer wifi. If this is true, then we can assure our customers that if infrastructure wifi is available at the venue, then with all devices connected to it, range will be adequate. If infrastructure wifi is not available at the venue, perhaps a mobile wifi router (battery operated) could be set up, devices connected to it, then range would be adequate. We are about to test this. Reasonable? Can we be assured that if infrastructure wifi is available, MC uses it? Regarding #2, given we are targeting minimum watchOS 7.0, would the available networking APIs and frameworks be adequate to implement our own equivalent of the MC framework so our app on iOS/iPadOS and watchOS devices could communicate? How much work? Where would I start? I'm new to implementing networking but experienced in using the MC framework. I'm assuming that I would write the networking code to use infrastructure wifi to achieve acceptable range. Many thanks! Tim
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1.8k
Sep ’25