What is the best way to detect if the Wifi is being used for Wireless Carplay or is just a normal network interface?

We are assisting a client with their app integration. The client believes that NEPacketTunnelProvider, NEHotspotHelper, and NEHotspotManager extensions stop functioning if the containing app hasn't been launched by the user within some recent window (e.g. 30, 60, or 90 days). We haven't been able to find any documentation supporting this claim. Specifically, we'd like to know: Is there any app launch recency requirement that would cause iOS to stop invoking a registered NEHotspotHelper or NEHotspotManager configuration? Is there any app launch recency requirement that would cause iOS to tear down or prevent activation of a NEPacketTunnelProvider? More generally, does iOS enforce any kind of "staleness" check on apps that provide Network Extension or Hotspot-related functionality, where not being foregrounded for some period causes the system to stop honoring their registrations? If such a mechanism exists, we'd appreciate any pointers to documentation or technical notes describing the behavior and timeframes involved. If it doesn't exist, confirmation would help us guide our client's debugging in the right direction. Thank you.

I'm a long-time developer, but pretty new to Swift. I'm trying to get information from a web service (and found code online that I adjusted to build the function below). (Note: AAA_Result -- referenced towards the end -- is another class in my project) Trouble is, I'm getting the subject error on the call to session.dataTask. Any help/suggestions/doc pointers will be greatly appreciated!!! var result: Bool = false var cancellable: AnyCancellable? self.name = name let params = "json={\"\"}}" // removed json details let base_url = URL(string: "https://aaa.yyy.com?params=\(params)&format=json")! // removed URL specifics do { let task = URLSession.shared.dataTask(with: base_url) { data, response, error in if let error = error { print("Error: \(error)") } guard let response = response as? HTTPURLResponse, (200...299).contains(response.statusCode) else { print("Error \(String(describing: response))") } do { let decoder = JSONDecoder() let ar = try decoder.decode(AAA_Result.self, from: response.value) // removed specific details... result = true } catch { print(error) } } task.resume() } catch { print(error) } return result }

Just bought a macbook pro m4, im trying to run an api on port 5000, disabled airplay receiver, checked processes, ghost ones, hidden ones, and stuck ones. I didn't find a thing using the port, but i still get port in use.

Hi everyone 👋 As a network engineer and indie iOS developer, I couldn’t find a lightweight mobile tool that fully supports IPv4/IPv6 dual-stack diagnostics — so I built NetToolbox -All-In-One Utility for engineers, DevOps, and developers. Here are its core features that solve real mobile networking pain points: One-Click Full Diagnostics: Integrates ping, traceroute, and multi-type DNS queries (A/AAAA/CNAME) — no need to switch between apps IPv4/IPv6 Dual-Stack Support: Seamlessly works in IPv6-only networks, with the ability to test connectivity differences between dual-stack environments LAN Device Scanning: Quickly identifies all devices on the same network segment and checks port availability Offline Functionality: Diagnostic logic is stored locally, enabling LAN troubleshooting without an internet connection Lightweight Design: 5MB install size, no storage bloat, and low power consumption during operation Dark Mode Support: Tailored for developers who work late at night During development, I leveraged Apple Intelligence alongside Claude Code and Gemini 3 to accelerate the process, optimize iOS native networking stack adaptation and local storage logic, and significantly boost development efficiency. I’d love to hear from the community: What must-have features are missing from mobile network diagnostic tools? Do you have experience optimizing iOS workflows with Apple Intelligence? 👉 You can try the app here: https://apps.apple.com/us/app/nettoolbox-all-in-one-utility/id6757392404 Feedback is highly appreciated — I’ll keep iterating to make it better! 🚀

Hi, I am making a AI-Powered app that makes api requests to the openai API. However, for security, I set up a vercel backend that handles the API calls securely, while my frontend makes a call to my vercel-hosted https endpoint. Interestingly, whenever I try to make that call on my device, an iPhone, I get this error: Task <91AE4DE0-2845-4348-89B4-D3DD1CF51B65>.<10> finished with error [-1003] Error Domain=NSURLErrorDomain Code=-1003 "A server with the specified hostname could not be found." UserInfo={_kCFStreamErrorCodeKey=-72000, NSUnderlyingError=0x1435783f0 {Error Domain=kCFErrorDomainCFNetwork Code=-1003 "(null)" UserInfo={_kCFStreamErrorDomainKey=10, _kCFStreamErrorCodeKey=-72000, _NSURLErrorNWResolutionReportKey=Resolved 0 endpoints in 3ms using unknown from query, _NSURLErrorNWPathKey=satisfied (Path is satisfied), interface: pdp_ip0[lte], ipv4, ipv6, dns, expensive, uses cell}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <91AE4DE0-2845-4348-89B4-D3DD1CF51B65>.<10>, _NSURLErrorRelatedURLSessionTaskErrorKey=( "LocalDataTask <91AE4DE0-2845-4348-89B4-D3DD1CF51B65>.<10>" ), NSLocalizedDescription=A server with the specified hostname could not be found., NSErrorFailingURLStringKey=https://[my endpoint], NSErrorFailingURLKey=https://[my endpoint], _kCFStreamErrorDomainKey=10} I'm completely stuck because when I directly make https requests to other api's like openai's endpoint, without the proxy, it finds the server completely fine. Running my endpoint on terminal with curl also works as intended, as I see api key usages. But for some reason, on my project, it does not work. I've looked through almost every single post I could find online, but a lot all of the solutions are outdated and unhelpful. I'm willing to schedule a call, meeting, whatever to resolve this issue and get help more in depth as well.

We are having an issue with the Local Network permission pop-up not getting triggered for our apps that need to communicate with devices via local network interfaces/addresses. As we understand, apps using UDP should trigger this, causing macOS to prompt for access, or, if denied, fail to connect. However, we are facing issues with macOS not prompting this popup at all. Here are important and related points: Our application is packaged as a .app package and distributed independently (not on the App Store). The application controls hardware that we manufacture. In order to find the hardware on the network, we send a UDP broadcast with a message for our hardware on the local network, and the hardware responds with a message back. However, the popup (to ask for permission) never shows up. The application is not able to find the hardware device. It is interesting to note that data is still sent out to the network (without the popup) but we receive back the wrong data. The behaviour is consistent macOS Sequoia (and above) with both Apple And Intel silicon. Workarounds that have been tried: Manual Authorization: One solution suggested in various blogs was to go to "Settings → Privacy and Security-> Local network", find your application and grant access. However, the application never shows up in the list here. Firewall: No difference is seen in behaviour with firewall being ON OR OFF. Setting NSLocalNetworkUsageDescription: We have also tried setting the Info.plist adding the NSLocalNetworkUsageDescription with a meaningful string and updating the NSBonjourServices. Running Via terminal (WORKS): Running the application via terminal sees no issues. The application runs correctly and is able to send UDP and receive correct data (and find the devices on the network). But this is not an appropriate solution. How can we get this bug/issue fixed in macOS Sequoia (and above)? Are there any other solutions/workarounds that we can try on our end?

Before iOS16, we can use https://developer.apple.com/documentation/coretelephony/ctcarrier But after iOS this is deprecated and has no replacement. There are some discussions on it, eg. https://developer.apple.com/forums/thread/714876 https://developer.apple.com/forums/thread/770400 Now I asked AI, then it provided this solution, to check the serviceCurrentRadioAccessTechnology, so it this ok to check the SIM card status? var hasSIMCard = false let info = CTTelephonyNetworkInfo() if let rat = info.serviceCurrentRadioAccessTechnology, rat.values.contains(where: { !$0.isEmpty }) { hasSIMCard = true. // has RAT } BTW, I can see a lot of changes in the Core Telephony framework. https://developer.apple.com/documentation/coretelephony 1.isSIMInserted https://developer.apple.com/documentation/coretelephony/ctsubscriber/issiminserted A Boolean property that indicates whether a SIM is present. iOS 18.0+ iPadOS 18.0+ This value property is true if the system finds a SIM matching the Info.plist carrier information (MCC / MNC / GID1 / GID2). Is this ok to check SIM insert status, this seems must preconfig some info in the info.plist. 2.iOS26 provide CTCellularPlanStatus https://developer.apple.com/documentation/coretelephony/ctcellularplanstatus Can I use this to check SIM status?

Hello, I have encountered an issue with an iPhone 15PM with iOS 18.5. The NSHTTPCookieStorage failed to clear cookies, but even after clearing them, I was still able to retrieve them. However, on the same system It is normal on iPhone 14PM. I would like to know the specific reason and whether there are any adaptation related issues. Following code: NSHTTPCookie *cookie; NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage]; for (cookie in [storage cookies]) { [storage deleteCookie:cookie]; }

multicast sockets fail to send/receive on macosx, errno 65 "no route to host". Wireshark and Terminal.app (which have root privileges) both show incoming multicast traffic just fine. Normal UDP broadcast sockets have no problems. Toggling the Security&Privacy -> Local Network setting may fix the problem for some Users. There is no pattern for when multicast socket fails. Sometimes, recreating the sockets fix the problem. Restart the app, sometimes multicast fails, sometimes success (intermittent, no pattern). Reboot machine (intermittent fail) Create a fresh new user on machine, install single version of app, give app permission. (intermittent fail, same as above). We have all the normal entitlements / notarized app. Similar posts here see FB16923535, Related to FB16512666 https://forum.xojo.com/t/udp-multicast-receive-on-mac-failing-intermittant/83221 see my post from 2012 "distinguishing between SENDING sockets and RECEIVING sockets" for source code example of how we bind multicast sockets. Our other socket code is standard "Stevens, et al." code. The bind() is the call that fails in this case. https://stackoverflow.com/questions/10692956/what-does-it-mean-to-bind-a-multicast-udp-socket . Note that this post from 2012 is still relevant, and that it is a workaround to a longstanding Apple bug that was never fixed. Namely, "Without this fix, multicast sending will intermittently get sendto() errno 'No route to host'. If anyone can shed light on why unplugging a DHCP gateway causes Mac OS X multicast SENDING sockets to get confused, I would love to hear it." This may be a hint as to the underlying bug that Apple really needs to fix, but if it's not, then please Apple, fix the Sequoia bug first. These are probably different bugs because in one case, sendto() fails when a socket becomes "unbound" after you unplug an unrelated network cable. In this case, bind() fails, so sendto() is never even called. Note, that we have also tried to use other implementations for network discovery, including Bonjour, CFNetwork, etc. Bonjour fails intermittently, and also suffers from both bugs mentioned above, amongst others.

Every now and again I end up helping a developer with a Wi-Fi issue. These fall into two groups: User-level Wi-Fi issues Development Wi-Fi issues A user-level Wi-Fi issue is one where the developer hasn’t created any of the products involved. An example of this is when you’re developing an app for an accessory and iOS is having problems connecting to that accessory but you don’t control the accessory’s firmware. In general, I recommend that you escalate such issues to the accessory vendor. They can then run their own investigation and, if necessary, file their own bug report. A development Wi-Fi issue is one that directly affects one of your products. For example, you’re developing a Wi-Fi accessory and iOS is having problems connecting to it. In that case, the onus is on you [1] to investigate why things are failing. If your conclusion is that iOS is behaving incorrectly, file a bug about that. IMPORTANT If you do file a bug in the context of some forums thread, please post your bug number to the thread, just for the record. When filing this sort of bug report it’s important to provide: Solid evidence that the problem is on the Apple side of the fence Enough information for Apple’s engineers to investigate it effectively Let’s start with that second point. If you can reproduce the problem reliably, install the Wi-Fi debug profile on your device, reproduce the problem, noting down a rough timestamp, and include the resulting logs and that timestamp in your bug report. Also, consider attaching a packet trace. There are three options here: Record a packet trace from the perspective of the Apple device. On iOS, use an RVI packet trace for this. Record a packet trace from the perspective of your accessory. Record a Wi-Fi level packet trace. You can do this from your Mac (see Recording a Wi-Fi Packet Trace) but it might be easier to do this with the infrastructure you used during the bring up of your accessory. It’s fine to include all three (-: Also include any relevant context about the issue. For example: If the issue is tied to a specific device model (In that case, it’d be good to include the above information for both the successful and failing cases.) If the problem shows up when joining from Settings > Wi-Fi, or whether it’s tied to a specific API, like NEHotspotConfigurationManager Finally, make sure to include an explanation of why you think this is an Apple bug, referencing specific items in the logs and packet traces that you attached. Of course, it’s only possible to do all of this if you can reproduce the problem. Investigating an intermittent issue based on reports coming in from users is much harder. It’s OK to file a bug about such issues, but your bug might not be actionable. At a minimum you should aim to include a sysdiagnose log with your bug. IMPORTANT This log has to be taken shortly after reproducing the problem. Don’t just attach any old log. One option is to request such a log from your users. I talk more about this in Using a Sysdiagnose Log to Debug a Hard-to-Reproduce Problem. You can also ask your users to file their own bugs using the Feedback Assistant app. It should automatically capture and attach a sysdiagnose log. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" [1] Well, your organisation. It’s rare to find a team where the same engineer works on both the iOS app and the accessory firmware. But if that’s you, good job!

My team is developing an enterprise VPN application that needs to respond to Mobile Device Management (MDM) profile installations and removals in real-time. Our app uses the NetworkExtension framework and needs to update the UI immediately when VPN configurations are added or removed via MDM. We are currently observing NEVPNConfigurationChangeNotification to detect VPN configuration changes: While NEVPNConfigurationChangeNotification fires reliably when users manually remove VPN profiles through Settings > General > VPN & Device Management, it appears to have inconsistent behavior when MDM profiles containing VPN configurations are installed programmatically via MDM systems. STEPS TO REPRODUCE From MDM Admin Console: Deploy a new VPN profile to the test device On Device: Wait for MDM profile installation (usually silent, no user interaction required) Check Device Settings: Go to Settings > General > VPN & Device Management to confirm profile is installed Return to App: Check if the UI shows the new VPN profile

Are the network relays introduced in 2023 and https://developer.apple.com/videos/play/wwdc2023/10002/ the same thing as the Private Relay introduced in 2021? https://developer.apple.com/videos/play/wwdc2021/10096/ We are considering verifying the relay function, but we are not sure whether they are the same function or different functions. https://developer.apple.com/documentation/devicemanagement/relay?language=objc

We are using Multipeer Connectivity (MCSession, MCNearbyServiceBrowser, MCNearbyServiceAdvertiser) for nearby peer discovery and communication. **Observed behaviour: ** When Wi-Fi is ON (Not connected to any network) and Mobile Data is also ON: Peer discovery (foundPeer) consistently succeeds Invitation is sent using invitePeer MCSession transitions to .connecting The session remains indefinitely in .connecting connected is never reached notConnected is also not reported When Mobile Data is turned OFF, the same flow reliably reaches .connected. Key details: Both devices have Wi-Fi and Bluetooth enabled Browsing and advertising are active on both devices Application-level timeouts and session resets are implemented The Issue is reproducible across multiple devices with iOS 26 versions. Expectation / Question: We understand that Multipeer Connectivity does not use cellular data for peer discovery or transport. However, when Wi-Fi is available and peers are discovered successfully, we would like clarification on the following: Is it expected behavior that enabling Mobile Data can cause the invitation/connection phase to remain indefinitely in .connecting without transitioning to .notConnected? Are there recommended best practices to avoid stalled invitation or transport negotiation in this scenario? Is there a supported way to detect or recover from a stalled .connecting state beyond application-level timeouts and session resets? Any guidance on expected behavior or recommended handling would be appreciated.

cant open this website: https://appstoreconnect.apple.com/apps  Bad Gateway Correlation Key: EJMQBY3TQQI6QR2RBCFRFK7WSM

I develop a Network Extension with NEFilterDataProvider and want to understand how to stop or disable it on exit of the base app without deactivating NE from OS and leave ability to start it again without requiring a password from the user. It starts normally, but when I try to disable it: NEFilterManager.sharedManager.enabled = NO; [NEFilterManager.sharedManager saveToPreferencesWithCompletionHandler:^(NSError * _Nullable error) { // never called }]; the completion handler has never called. But stopFilterWithReason inside the NE code called by the framework where I only replay with required completionHandler();. Then NE process keeps alive. I also tried to call remove, which should disable NE: [NEFilterManager.sharedManager removeFromPreferencesWithCompletionHandler:^(NSError * _Nullable error) { // never called }]; with same result - I freeze forever on waiting completion handler. So what is the correct way to disable NE without explicit deactivation it by [OSSystemExtensionRequest deactivationRequestForExtension:...]?

Error 8 in the NEHotspotConfigurationError domain is .internal, aka NEHotspotConfigurationErrorInternal. This error typically indicates that something went wrong in some sort of expected way, but we decided not to surface the exact cause [1]. This has come up a bunch of times before on the forums, and I have various titbits to share. To start, I want to address some specific cases: You’ll see this error if your app isn’t signed with the com.apple.developer.networking.HotspotConfiguration entitlement. To fix this, use Xcode’s Signing & Capabilities editor to add the Hotspot capability to your app. Historically developers reported a situation where once they encountered the error it would show up consistently, but then it would go away on restarting the device. If you see behaviour like that, that’s definitely a bug and I encourage you to file it as such. I have more about filing such bugs in Filing a Wi-Fi Bug Report. Of course, you have to wait to reproduce the error again before you’ll be able to file that bug, because the act of restarting cleared the issue. I’ve seen reports where such problems only occur on a specific type of device, for example, on iPhone 16 but not on earlier or later iPhones. That’s definitely something that Apple should investigate, and I recommend that you file a bug about it. If the problem is being reported by your users but you can’t reproduce it yourself, consider the various suggestions in Using a Sysdiagnose Log to Debug a Hard-to-Reproduce Problem. Assuming you’re still here (-: the next step is to determine whether the problem is specific to NEHotspotConfigurationManager or not. Try joining the accessory’s network from Settings > Wi-Fi. Does that also have problems? If so, that’s not something we can help you with here on the forums. The focus of the Apple Developer Forums is primarily to help developers with the APIs in Apple’s various platform SDKs [2]. We’re not set up to help accessory developers with Wi-Fi issues. However, there are still things you can do, as I explain in Filing a Wi-Fi Bug Report. At this point you have an error that: Persists across restarts Happens with all Apple devices You can reproduce Only affects NEHotspotConfigurationManager If that’s correct then there are a couple of things you might look at: Coerce the error to an NSError and print that. Does it reveal anything interesting? Also check the underlying error property (NSUnderlyingErrorKey) for hints. When reproducing the error, monitor the system log for log entries in the com.apple.networkextension subsystem. Do those offer any clues? Note For lots of hints and tips about the system log, see Your Friend the System Log. And finally, if you have questions about this case, feel free to start a thread here on the forums and we’ll try to help you out. Put it in the App & System Services > Networking subtopic and tag it with Network Extension. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" [1] There’s also the .unknown error. See this post for a brief summary of the difference. [2] And with Apple tools and some developer-oriented services. Revision History 2026-03-18 Added a missing entitlement bullet to the specific case list. 2026-03-17 First posted.

Hi Apple Team / Community, We are currently pulling our hair out over a TestNet OTA issue and could really use some help. Our Matter Door Lock (VID: 5424, PID: 513) has already obtained official CSA Certification, so we are 100% confident that our device firmware and OTA Requestor logic are completely solid. However, we simply cannot get Apple's TestNet to serve the update via HomePod. Here is exactly what is happening: Our device successfully sends a QueryImage command to the HomePod. The HomePod receives it, but immediately fires back a QueryImageResponse that essentially means "UpdateNotAvailable", forcing the device into an 86400-second sleep timeout. Here is what we have verified so far: Local OTA works perfectly: If we use Nordic's chip-ota-provider-app locally with the exact same .ota file, the BDX transfer triggers instantly and the device updates without a hitch. DCL details are 100% accurate: We published a brand new version (1.0.4 / 16778240) which is strictly higher than the device's current version (1.0.1 / 16777472). The otaFileSize (973839) and Base64 Checksum match the file perfectly. ZERO hits on our server: The OTA file is hosted on an AWS S3 direct link (SSL Grade A via SSL Labs, ATS compliant). We checked our server logs, and there hasn't been a single download attempt from any Apple IP addresses. Since our device is certified and local OTA works flawlessly, it strongly feels like Apple's TestNet backend either has a stuck/cached "invalid" state for our VID/PID (very similar to what was reported in CHIP GitHub Issue #29338), or the Apple backend crawler is failing to reach our URL for some internal reason. Could someone please check if there is a cached exception for VID: 5424 / PID: 513 on the TestNet backend? Any help or pointers would be hugely appreciated! Thanks in advance.

IMPORTANT The resume rate limiter is now covered by the official documentation. See Use background sessions efficiently within Downloading files in the background. So, the following is here purely for historical perspective. NSURLSession’s background session support on iOS includes a resume rate limiter. This limiter exists to prevent apps from abusing the background session support in order to run continuously in the background. It works as follows: nsurlsessiond (the daemon that does all the background session work) maintains a delay value for your app. It doubles that delay every time it resumes (or relaunches) your app. It resets that delay to 0 when the user brings your app to the front. It also resets the delay to 0 if the delay period elapses without it having resumed your app. When your app creates a new task while it is in the background, the task does not start until that delay has expired. To understand the impact of this, consider what happens when you download 10 resources. If you pass them to the background session all at once, you see something like this: Your app creates tasks 1 through 10 in the background session. nsurlsessiond starts working on the first few tasks. As tasks complete, nsurlsessiond starts working on subsequent ones. Eventually all the tasks complete and nsurlsessiond resumes your app. Now consider what happens if you only schedule one task at a time: Your app creates task 1. nsurlsessiond starts working on it. When it completes, nsurlsessiond resumes your app. Your app creates task 2. nsurlsessiond delays the start of task 2 a little bit. nsurlsessiond starts working on task 2. When it completes, nsurlsessiond resumes your app. Your app creates task 3. nsurlsessiond delays the start of task 3 by double the previous amount. nsurlsessiond starts working on task 3. When it completes, nsurlsessiond resumes your app. Steps 8 through 11 repeat, and each time the delay doubles. Eventually the delay gets so large that it looks like your app has stopped making progress. If you have a lot of tasks to run then you can mitigate this problem by starting tasks in batches. That is, rather than start just one task in step 1, you would start 100. This only helps up to a point. If you have thousands of tasks to run, you will eventually start seeing serious delays. In that case it’s much better to change your design to use fewer, larger transfers. Note All of the above applies to iOS 8 and later. Things worked differently in iOS 7. There’s a post on DevForums that explains the older approach. Finally, keep in mind that there may be other reasons for your task not starting. Specifically, if the task is flagged as discretionary (because you set the discretionary flag when creating the task’s session or because the task was started while your app was in the background), the task may be delayed for other reasons (low power, lack of Wi-Fi, and so on). Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" (r. 22323366)

From time to time the subject of NECP grows up, both here on DevForums and in DTS cases. I’ve posted about this before but I wanted to collect those tidbits into single coherent post. If you have questions or comments, start a new thread in the App & System Services > Networking subtopic and tag it with Network Extension. That way I’ll be sure to see it go by. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" A Peek Behind the NECP Curtain NECP stands for Network Extension Control Protocol. It’s a subsystem within the Apple networking stack that controls which programs have access to which network interfaces. It’s vitally important to the Network Extension subsystem, hence the name, but it’s used in many different places. Indeed, a very familiar example of its use is the Settings > Mobile Data [1] user interface on iOS. NECP has no explicit API, although there are APIs that are offer some insight into its state. Continuing the Settings > Mobile Data example above, there is a little-known API, CTCellularData in the Core Telephony framework, that returns whether your app has access to WWAN. Despite having no API, NECP is still relevant to developers. The Settings > Mobile Data example is one place where it affects app developers but it’s most important for Network Extension (NE) developers. A key use case for NECP is to prevent VPN loops. When starting an NE provider, the system configures the NECP policy for the NE provider’s process to prevent it from using a VPN interface. This means that you can safely open a network connection inside your VPN provider without having to worry about its traffic being accidentally routed back to you. This is why, for example, an NE packet tunnel provider can use any networking API it wants, including BSD Sockets, to run its connection without fear of creating a VPN loop [1]. One place that NECP shows up regularly is the system log. Next time you see a system log entry like this: type: debug time: 15:02:54.817903+0000 process: Mail subsystem: com.apple.network category: connection message: nw_protocol_socket_set_necp_attributes [C723.1.1:1] setsockopt 39 SO_NECP_ATTRIBUTES … you’ll at least know what the necp means (-: Finally, a lot of NECP infrastructure is in the Darwin open source. As with all things in Darwin, it’s fine to poke around and see how your favourite feature works, but do not incorporate any information you find into your product. Stuff you uncover by looking in Darwin is not considered API. [1] Settings > Cellular Data if you speak American (-: [2] Network Extension providers can call the createTCPConnection(to:enableTLS:tlsParameters:delegate:) method to create an NWTCPConnection [3] that doesn’t run through the tunnel. You can use that if it’s convenient but you don’t need to use it. [3] NWTCPConnection is now deprecated, but there are non-deprecated equivalents. For the full story, see NWEndpoint History and Advice. Revision History 2025-12-12 Replaced “macOS networking stack” with “Apple networking stack” to avoid giving the impression that this is all about macOS. Added a link to NWEndpoint History and Advice. Made other minor editorial changes. 2023-02-27 First posted.