I observed the following crash: Code Type: ARM-64 (Native) Parent Process: launchd [1] User ID: 0 Date/Time: 2025-10-07 13:48:29.082 OS Version: macOS 15.6 (24G84) Report Version: 12 Anonymous UUID: 8B651788-4B2E-7869-516B-1DA0D60F3744 Crashed Thread: 3 Dispatch queue: NEFlow queue Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000054 ... Thread 3 Crashed: Dispatch queue: NEFlow queue 0 libdispatch.dylib 0x000000019af6da34 dispatch_async + 192 1 libnetworkextension.dylib 0x00000001b0cf8580 __flow_startup_block_invoke.216 + 124 2 com.apple.NetworkExtension 0x00000001adf97da8 __88-[NEExtensionAppProxyProviderContext setInitialFlowDivertControlSocket:extraValidation:]_block_invoke.90 + 860 3 libnetworkextension.dylib 0x00000001b0cf8140 __flow_startup_block_invoke.214 + 172 4 libdispatch.dylib 0x000000019af67b2c _dispatch_call_block_and_release + 32 5 libdispatch.dylib 0x000000019af8185c _dispatch_client_callout + 16 6 libdispatch.dylib 0x000000019af70350 _dispatch_lane_serial_drain + 740 7 libdispatch.dylib 0x000000019af70e2c _dispatch_lane_invoke + 388 8 libdispatch.dylib 0x000000019af7b264 _dispatch_root_queue_drain_deferred_wlh + 292 9 libdispatch.dylib 0x000000019af7aae8 _dispatch_workloop_worker_thread + 540 10 libsystem_pthread.dylib 0x000000019b11be64 _pthread_wqthread + 292 11 libsystem_pthread.dylib 0x000000019b11ab74 start_wqthread + 8 ... It appears that the crash is caused by the flow director queue becoming NULL when dispatch_async is called (accessing address 0x0000000000000054). Meanwhile, my transparent proxy was still running. I'm wondering if this is a known issue or if anyone else has encountered the same problem. @eskimo

on MacOS I am using raw socket and PF_Route options to monitor the routing table changes but looks like that is not supported in iOS what are the other ways to achieve real time monitoring in iOS ?

Hi, I have created an application for NFC tag scanning and read the tag data. For that, i enabled the capability: NearField Communication Tag reading. Then I added 2 tag formats in the entitlement then i added info.plist: NFCReaderUsageDescription We need to use NFC com.apple.developer.nfc.readersession.felica.systemcodes 8005 8008 0003 fe00 90b7 927a 12FC 86a7 com.apple.developer.nfc.readersession.iso7816.select-identifiers D2760000850100 D2760000850101 but even though when i run the app and tap the nfc card im getting some error: NFCTag didBecomeActive 2025-08-29 19:08:12.272278+0530 SAFRAN_NFC[894:113090] NFCTag didDetectTags 2025-08-29 19:08:12.282869+0530 SAFRAN_NFC[894:113520] [CoreNFC] -[NFCTagReaderSession _connectTag:error:]:730 Error Domain=NFCError Code=2 "Missing required entitlement" UserInfo={NSLocalizedDescription=Missing required entitlement} 2025-08-29 19:08:12.284044+0530 SAFRAN_NFC[894:113090] NFCTag restarting polling 2025-08-29 19:08:12.372116+0530 SAFRAN_NFC[894:113090] NFCTag didDetectTags 2025-08-29 19:08:12.381535+0530 SAFRAN_NFC[894:113378] [CoreNFC] -[NFCTagReaderSession _connectTag:error:]:730 Error Domain=NFCError Code=2 "Missing required entitlement" UserInfo={NSLocalizedDescription=Missing required entitlement} 2025-08-29 19:08:12.382246+0530 SAFRAN_NFC[894:113090] NFCTag restarting polling 2025-08-29 19:08:12.470667+0530 SAFRAN_NFC[894:113090] NFCTag didDetectTags 2025-08-29 19:08:12.479336+0530 SAFRAN_NFC[894:113378] [CoreNFC] -[NFCTagReaderSession _connectTag:error:]:730 Error Domain=NFCError Code=2 "Missing required entitlement" UserInfo={NSLocalizedDescription=Missing required entitlement} 2025-08-29 19:08:12.480101+0530 SAFRAN_NFC[894:113090] NFCTag restarting polling Could you please help me wha tis the issue and give solution for that?

I am developing an application that processes a video file stored on a server. I use URLSessionDataTask with a delegate handler to download the file. It is not necessary to download the entire file at once. Instead, I can load small chunks of the file as needed. This approach helps minimize memory consumption. I am trying to design a network layer that supports this behavior. Ideally, I would like to have an interface similar to: func readMoreData(length: Int) async throws -> Data Problems I Encountered: It seems that URLSessionDataTask does not allow controlling how many bytes will be downloaded. It always downloads the entire request. If I call suspend on URLSessionDataTask, the network activity does not stop, and the file keeps downloading. If I upgrade the dataTask to a StreamTask, the file still downloads, though reading bytes can be done through the StreamTask API. I would prefer behavior similar to AsyncHTTPClient (a Swift Server library) or Network Framework. These frameworks allow controlling the number of bytes downloaded at a time. Unfortunately, they do not fit the specific requirements of my project. Am I correct in understanding that controlling the download process is not possible with URLSessionDataTask? As a possible solution, I am considering using HTTP Range Requests, though this would increase the number of additional server requests, which I would like to avoid.

I’m developing a iOS VPN app, and I need to execute a task in the main app even when it’s in the background or killed state. I know the Network Extension continues running during those times. Is there a way for the extension to immediately notify the app or trigger a task on the app side?

Hello Everyone, I'm currently working on a cross-platform application that uses IP-based multicast for device discovery across both Apple and non-Apple devices running the same app. All devices join a multicast group "X.X.X.X" on port Y. For Apple devices, I am using NWConnectionGroup for multicast discovery, while for non-Apple devices, I am using BSD sockets. The issue arises when I attempt to send a multicast message to the group using NWConnectionGroup. The message is sent from a separate ephemeral port rather than the multicast port Y. As a result, all Apple processes that are using NWConnectionGroup can successfully receive the multicast message. However, the processes running on the non-Apple devices (using BSD sockets) do not receive the message. My Questions: Is there a way to configure NWConnectionGroup to send multicast messages from the same multicast port Y rather than an ephemeral port? Is there any known behavior or limitation in how NWConnectionGroup handles multicast that could explain why non-Apple devices using BSD sockets cannot receive the message? How can I ensure cross-platform multicast compatibility between Apple devices using NWConnectionGroup and non-Apple devices using BSD sockets? Any guidance or suggestions would be greatly appreciated! Thanks, Harshal

Hi, I observed some unexpected behavior and hope that someone can enlighten me as to what this is about: mDNSResponder prepends IP / network based default search domains that are checked before any other search domain. E.g. 0.1.168.192.in-addr.arpa. would be used for an interface with an address in the the 192.168.1.0/24 subnet. This is done for any configured non-link-local IP address. I tried to find any mention of an approach like this in RFCs but couldn't spot anything. Please note that this is indeed a search domain and different from reverse-DNS lookups. Example output of tcpdump for ping devtest: 10:02:13.850802 IP (tos 0x0, ttl 64, id 43461, offset 0, flags [none], proto UDP (17), length 92) 192.168.1.2.52319 > 192.168.1.1.53: 54890+ [1au] A? devtest.0.1.168.192.in-addr.arpa. (64) I was able to identify the code that adds those default IP subnet based search domains but failed to spot any indication as to what this is about: https://github.com/apple-oss-distributions/mDNSResponder/blob/d5029b5/mDNSMacOSX/mDNSMacOSX.c#L4171-L4211 Does anyone here have an ideas as to what this might be about?

We are using PacketTunnel as system extension to establish vpn tunnel. The flow is like: Create a PacketTunnelProvide to establish vpn When tunnel gets connected add excludedRoutes by calling setTunnelNetworkSettings(). Result: The routing table is not getting updated with new excludeRoutes entries. As per setTunnelNetworkSettings() documentation: "This function is called by tunnel provider implementations to set the network settings of the tunnel, including IP routes, DNS servers, and virtual interface addresses depending on the tunnel type. Subclasses should not override this method. This method can be called multiple times during the lifetime of a particular tunnel. It is not necessary to call this function with nil to clear out the existing settings before calling this function with a non-nil configuration." So we believe setTunnelNetworkSettings() should be able to set new excludeRoutes. We could see we are passing correct entries to setTunnelNetworkSettings(): { tunnelRemoteAddress = 10.192.229.240 DNSSettings = { protocol = cleartext server = ( 10.192.230.211, 192.168.180.15, ) matchDomains = ( , ) matchDomainsNoSearch = NO } IPv4Settings = { configMethod = manual addresses = ( 100.100.100.17, ) subnetMasks = ( 255.255.255.255, ) includedRoutes = ( { destinationAddress = 1.1.1.1 destinationSubnetMask = 255.255.255.255 gatewayAddress = 100.100.100.17 }, { destinationAddress = 2.2.2.0 destinationSubnetMask = 255.255.255.255 gatewayAddress = 100.100.100.17 }, { destinationAddress = 11.11.11.0 destinationSubnetMask = 255.255.255.0 gatewayAddress = 100.100.100.17 }, ) excludedRoutes = ( { destinationAddress = 170.114.52.2 destinationSubnetMask = 255.255.255.255 }, ) overridePrimary = NO } MTU = 1298 } The problem is present on macOS Sequoia 15.2. Is it a known issue? Did anyone else faced this issue?

I'm trying to use NEHotspotNetwork to configure an IoT. I've read all the issues that have plagued other developers when using this framework, and I was under the impression that bugs were filed and fixed. Here are my issues in hopes that someone can catch my bug, or has finally figured this out and it's not a bug in the framework with no immediate fix on the horizon. If I use the following code: let config = NEHotspotConfiguration(ssid: ssid) config.joinOnce = true KiniStatusBanner.shared.show(text: "Connecting to Kini", in: presentingVC.view) NEHotspotConfigurationManager.shared.apply(config) { error in DispatchQueue.main.async { if let nsError = error as NSError?, nsError.domain == NEHotspotConfigurationErrorDomain, nsError.code == NEHotspotConfigurationError.alreadyAssociated.rawValue { print("Already connected to \(self.ssid)") KiniStatusBanner.shared.dismiss() self.presentCaptivePortal(from: presentingVC, activationCode: activationCode) } else if let error = error { // This doesn't happen print("❌ Failed to connect: \(error.localizedDescription)") KiniStatusBanner.shared.update(text: "Failed to Connect to Kini. Try again later.") KiniStatusBanner.shared.dismiss(after: 2.5) } else { // !!!! Most often, this is the path the code takes NEHotspotNetwork.fetchCurrent { current in if let ssid = current?.ssid, ssid == self.ssid { log("✅✅ 1st attempt: connected to \(self.ssid)") KiniStatusBanner.shared.dismiss() self.presentCaptivePortal(from: presentingVC, activationCode: activationCode) } else { // Dev forums talked about giving things a bit of time to settle and then try again DispatchQueue.main.asyncAfter(deadline: .now() + 2) { NEHotspotNetwork.fetchCurrent { current in if let ssid = current?.ssid, ssid == self.ssid { log("✅✅✅ 2nd attempt: connected to \(self.ssid)") KiniStatusBanner.shared.dismiss() self.presentCaptivePortal(from: presentingVC, activationCode: activationCode) } else { log("❌❌❌ 2nd attempt: Failed to connect: \(self.ssid)") KiniStatusBanner.shared.update(text: "Could not join Kini network. Try again.") KiniStatusBanner.shared.dismiss(after: 2.5) self.cleanupHotspot() DispatchQueue.main.asyncAfter(deadline: .now() + 2) { print("cleanup again") self.cleanupHotspot() } } } } log("❌❌ 1st attempt: Failed to connect: \(self.ssid)") KiniStatusBanner.shared.update(text: "Could not join Kini network. Try again.") KiniStatusBanner.shared.dismiss(after: 2.5) self.cleanupHotspot() } As you can see, one can't just use NEHotspotConfigurationManager.shared.apply and has to double-check to make sure that it actually succeeds, by checking to see if the SSID desired, matches the one that the device is using. Ok, but about 50% of the time, the call to NEHotspotNetwork.fetchCurrent gives me this error: NEHotspotNetwork nehelper sent invalid result code [1] for Wi-Fi information request Well, there is a workaround for that randomness too. At some point before calling this code, one can: let locationManager = CLLocationManager() locationManager.requestWhenInUseAuthorization() That eliminates the NEHotspotNetwork nehelper sent invalid result code [1] for Wi-Fi information request BUT... three issues. The user is presented with an authorization alert: Allow "Kini" to use your location? This app needs access to you Wi-Fi name to connect to your Kini device. Along with a map with a location pin on it. This gives my users a completely wrong impression, especially for a device/app where we promise users not to track their location. They actually see a map with their location pinned on it, implying something that would freak out anyone who was expecting no tracking. I understand why an authorization is normally required, but since all we are getting is our own IoT's SSID, there should be no need for an authorization for this, and no map associated with the request. Again, they are accessing my IoT's network, NOT their home/location Wi-Fi SSID. My app already knows and specifies that network, and all I am trying to do is to work around a bug that makes it look like I have a successful return from NEHotspotConfigurationManager.shared.apply() when in fact the network I was looking for wasn't even on. Not only do I get instances where the network doesn't connect, and result codes show no errors, but I also get instances where I get an alert that says that the network is unreachable, yet my IoT shows that the app is connected to its Wi-Fi. On the iOS device, I go to the Wi-Fi settings, and see that I am on the IoT's network. So basically, sometimes I connect, but the frameworks says that there is no connection, and sometimes it reports a connection when there is none. As you can see in the code, I call cleanupHotspot() to make the iOS device get off of my temp Wi-Fi SSID. This is the code: func cleanupHotspot() { NEHotspotConfigurationManager.shared.removeConfiguration(forSSID: ssid) } That code gets called by the above code when things aren't as I expect and need to cleanup. And I also call it when the user dismisses the viewcontroller that is attempting to make the connection. It doesn't always work. I get stuck on the tempo SSID, unless I go through this whole thing again: try to make the connection again, this time it succeeds quickly, and then I can disconnect. Any ideas? I'm on iOS18.5, and have tried this on multiple iPhones including 11, 13 and 16.

Hello team, Would this mean that content filters intended for all browsing can only be implemented for managed devices using MDM? My goal would be to create a content filtering app for all users, regardless of if their device is managed/supervised. thanks.

We are observing a reproducible issue on some (not all) iPad models equipped with A16, where BLE streaming from multiple peripherals at ≥33–40 Hz results in uneven packet distribution, burst delivery, and application-level lag. The same application, peripherals, firmware, iOS version, and physical environment do not exhibit this behaviour on A14-based iPads (iPad 10). Affected Hardware: • iPad 11" with A16 • iOS versions: identical across tested devices • Issue affects some devices of the same model, not all Internal field data • ~25 affected • ~5 unaffected • Customers actively prefer iPad 10 (A14) due to stability When two or more BLE peripherals stream data concurrently at frequencies ≥33–40 Hz, affected iPads exhibit: • Uneven packet arrival timing • Burst delivery instead of uniform intervals • Increasing latency over time • Observable application-level lag This does not present as simple packet loss. Instead, packets arrive in clusters, breaking real-time assumptions. At ≤30–33 Hz, the issue does not reproduce. We tested: • One affected iPad 11 • One unaffected iPad 11 • Same iOS version • Same app build • Same peripherals • Same firmware • Same physical location • Same Wi-Fi state Only the affected device reproduces the issue. This rules out: • App logic • Peripheral firmware • iOS version • Environmental RF noise • Wi-Fi coexistence configuration Evidence Available We can provide: • Screenshots from a minimal test app showing packet counts • CSV files of packet timestamps • Source code for the BLE test app • Side-by-side comparison logs (affected vs unaffected device) All evidence is from the same app, built solely to measure packet timing. Additional Technical Notes • Issue persists after factory reset • Occurs without third-party BLE libraries (CoreBluetooth only) • Occurs regardless of foreground/background state • Not correlated with MTU size • Appears threshold-based (~33–40 Hz) • Appears device-specific, not model-wide

Hi, I have a problem about "NSPOSIXErrorDomain Code=65 & iOS18 & Xcode 16". I used 'CocoaAsyncSocket', '~> 7.6.5'. It works fine on iOS 15.2， But it's worried on iOS 18.3. Before this, broadcasts can be obtained normally。 I had get socket Multicast Networking. Please help me .

Hello, I'm working on a Transparent Proxy and when the proxy is being stopped, I'm stopping all the flows by calling flow.closeWriteWithError(POSIXError(.ECANCELED)) flow.closeReadWithError(POSIXError(.ECANCELED)) Then all the flows are deallocated. When deallocating the flow the crash occurs: OS Version: macOS 14.1.2 (23B92) Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000001, 0x000000018c2ef704 Termination Reason: Namespace SIGNAL, Code 5 Trace/BPT trap: 5 Terminating Process: exc handler [553] Thread 32 Crashed:: Dispatch queue: <my dispatch queue> 0 CoreFoundation 0x18c2ef704 CF_IS_OBJC + 76 1 CoreFoundation 0x18c23f61c CFErrorGetDomain + 32 2 libnetworkextension.dylib 0x19fe56a00 flow_error_to_errno + 28 3 libnetworkextension.dylib 0x19fe56920 flow_handle_pending_write_requests + 216 4 libnetworkextension.dylib 0x19fe5667c __NEFlowDeallocate + 380 5 CoreFoundation 0x18c2efe28 _CFRelease + 292 6 NetworkExtension 0x19d208390 -[NEAppProxyFlow dealloc] + 36 Is there any way to debug what is happening and if it's related to closing the flow with POSIXError? Thank you

I am currently developing a custom-protocol VPN application for iOS using PacketTunnelProvider. I have also integrated an HTTP proxy service, which is launched via a dylib. The overall flow is as follows: App -> VPN TUN -> Local HTTP Proxy -> External Network I have a question: I am capturing all traffic, and normally, requests sent out by the HTTP proxy are also captured again by the VPN. However, when I send requests using createUdpSession in my code, they are not being captured by the virtual interface (TUN). What could be the reason for this? override func startTunnel(options: [String : NSObject]?, completionHandler: @escaping (Error?) -> Void) { let tunnelNetworkSettings = NEPacketTunnelNetworkSettings(tunnelRemoteAddress: "192.168.18.0") tunnelNetworkSettings.mtu=1400 let ipv4Settings = NEIPv4Settings(addresses: ["192.169.10.10"], subnetMasks: ["255.255.255.0"]) ipv4Settings.includedRoutes=[NEIPv4Route.default()] ipv4Settings.excludedRoutes = [NEIPv4Route(destinationAddress: "10.0.0.0", subnetMask: "255.0.0.0"), NEIPv4Route(destinationAddress: "172.16.0.0", subnetMask: "255.240.0.0"), NEIPv4Route(destinationAddress: "192.168.0.0", subnetMask: "255.255.0.0"), NEIPv4Route(destinationAddress:"127.0.0.0", subnetMask: "255.0.0.0"), ] tunnelNetworkSettings.ipv4Settings = ipv4Settings // Configure proxy settings let proxySettings = NEProxySettings() proxySettings.httpEnabled = true proxySettings.httpServer = NEProxyServer(address: "127.0.0.1", port: 7890) proxySettings.httpsEnabled = true proxySettings.httpsServer = NEProxyServer(address: "127.0.0.1", port: 7890) proxySettings.excludeSimpleHostnames = true proxySettings.exceptionList=["localhost","127.0.0.1"] tunnelNetworkSettings.proxySettings = proxySettings setTunnelNetworkSettings(tunnelNetworkSettings) { [weak self] error in if error != nil { completionHandler(error) return } completionHandler(nil) let stack = TUNInterface(packetFlow: self!.packetFlow) RawScoketFactory.TunnelProvider=self stack.register(stack: UDPDirectStack()) stack.register(stack: TCPDirectStack()) stack.start() } } NWUdpSession.swift // // NWUDPSocket.swift // supervpn // // Created by TobbyQuinn on 2025/2/3. // import Foundation import NetworkExtension import CocoaLumberjack public protocol NWUDPSocketDelegate: AnyObject{ func didReceive(data:Data,from:NWUDPSocket) func didCancel(socket:NWUDPSocket) } public class NWUDPSocket:NSObject{ private let session:NWUDPSession private let timeout:Int private var pendingWriteData: [Data] = [] private var writing = false private let queue:DispatchQueue=QueueFactory.getQueue() public weak var delegate:NWUDPSocketDelegate? public init?(host:String,port:UInt16,timeout:Int=Opt.UDPSocketActiveTimeout){ guard let udpSession = RawScoketFactory.TunnelProvider?.createUDPSession(to: NWHostEndpoint(hostname: host, port: "\(port)"), from: nil) else{ return nil } session = udpSession self.timeout=timeout super.init() session.addObserver(self, forKeyPath: #keyPath(NWUDPSession.state),options: [.new], context: nil) session.setReadHandler({ dataArray, error in self.queueCall{ guard error == nil, let dataArray = dataArray else { print("Error when reading from remote server or connection reset") return } for data in dataArray{ self.delegate?.didReceive(data: data, from: self) } } }, maxDatagrams: 32) } /** Send data to remote. - parameter data: The data to send. */ public func write(data: Data) { pendingWriteData.append(data) checkWrite() } public func disconnect() { session.cancel() } public override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { guard keyPath == "state" else { return } switch session.state { case .cancelled: queueCall { self.delegate?.didCancel(socket: self) } case .ready: checkWrite() default: break } } private func checkWrite() { guard session.state == .ready else { return } guard !writing else { return } guard pendingWriteData.count > 0 else { return } writing = true session.writeMultipleDatagrams(self.pendingWriteData) {_ in self.queueCall { self.writing = false self.checkWrite() } } self.pendingWriteData.removeAll(keepingCapacity: true) } private func queueCall(block:@escaping ()->Void){ queue.async { block() } } deinit{ session.removeObserver(self, forKeyPath: #keyPath(NWUDPSession.state)) } }

I use eapolcfg in Apple's open source eap8021x repository to connect to the enterprise network. 1.https://github.com/gfleury/eap8021x-debug https://opensource.apple.com/source/eap8021x/eap8021x-304.100.1/ Our enterprise network authentication is PEAP. So far, I have created a profile using the following commands and have done the access. ./eapolcfg createProfile --authType PEAP --SSID myssid --securityType WPA2 --userDefinedName MyProfile ./eapolcfg setPasswordItem --password mypassword --name myname --SSID myssid ./eapolcfg startAuthentication --interface en0 --SSID myssid After I performed this series of operations, I passed BOOL success = [self.interface associateToEnterpriseNetwork:network identity:nil username:username password:password error:&amp;error]; Connection will pop up the following pop-up window, sometimes associateToEnterpriseNetwork will fail. I don't know what went wrong, is it that I missed some steps through the eapolcfg [tool?] This function also reports the following error：Error Domain=com.apple.coreWLAN.EAPOL.error Code=1 "(null)" Please answer my questions. Thank you very much

Esim activation. Assuming I already have card data, I use the universal link https://esimsetup.apple.com/esim_qrcode_provisioning?carddata= to install it. However, it always ends up in the system Settings app. The flow: 1. Click the link -&gt; 2. Redirect to Settings -&gt; 3. Show activation dialog. Is there anyway to make the activation flow stay within the app? I couldn't find any documentation for that. This is an example from Revolut app, where the whole flow above happens without leaving the app.

We have an iOS companion app that talks to our IoT device over the device’s own Wi‑Fi network (often with no internet). The app performs bi-directional, safety-critical duties over that link. We use an NEAppPushProvider extension so the handset can keep exchanging data while the UI is backgrounded. During testing we noticed that if the user backgrounds the app (still connected to the device’s Wi‑Fi) and opens Safari, the extension’s stop is invoked with NEProviderStopReason.unrecoverableNetworkChange / noNetworkAvailable, and iOS tears the extension down. Until the system restarts the extension (e.g. the user foregrounds our app again), the app cannot send/receive its safety-critical data. Questions: Is there a supported way to stop a safety-critical NEAppPushProvider from being terminated in this “background app → open Safari” scenario when the device remains on the same Wi‑Fi network (possibly without internet)? If not, is NEAppPushProvider the correct extension type for an always-on local-network use case like this, or is there another API we should be using? For safety-critical applications, can Apple grant entitlements/exemptions so the system does not terminate the extension when the user switches apps but stays on the local Wi‑Fi? Any guidance on the expected lifecycle or alternative patterns for safety-critical local connectivity would be greatly appreciated.

Hi, when I perform an overlay installation via a PKG on macOS for an application containing the NEFilterDataProvider functionality, there is a chance that the entire system network becomes unreachable. Disabling the corresponding Content Filter in "System Settings > Network > Filters" immediately restores network connectivity. This issue does not occur every time, with a frequency of approximately 1 in 20 installation attempts.  The following details may help identify the problem: The Filter.app containing the NEFilterDataProvider resides within the main app's Resources directory, e.g., /Applications/Main.app/Contents/Resources/Filter.app Main.app is installed via a PKG; the issue typically occurs during an overlay installation of Main.app. The NEFilterDataProvider operates as a System Extension. The func handleNewFlow(_ flow: NEFilterFlow) -> NEFilterNewFlowVerdict {} returns .allow. Wireshark packet captures show TCP packets but no UDP packets; TCP handshakes cannot complete. Disabling the corresponding content filter in "System Settings > Network > Filters" restores the network; re-enabling it breaks connectivity again. After waiting for a period, approximately 30-60 minutes, network connectivity can recover automatically. What causes this and how can it be fixed? Any workarounds?

My external device can generate a fixed Wi-Fi network. When I connect to this Wi-Fi using my iPhone 17 Pro Max (iOS version 26.0.1), and my app tries to establish a connection using the following method, this method returns -1 int connect(int, const struct sockaddr *, socklen_t) __DARWIN_ALIAS_C(connect); However, when I use other phones, such as iPhone 12, iPhone 8, iPhone 11, etc., to connect to this external device, the above method always returns successfully, with the parameters passed to the method remaining the same. I also tried resetting the network settings on the iPhone 17 Pro Max (iOS version 26.0.1), but it still cannot establish a connection.

Questions about FTP crop up from time-to-time here on DevForums. In most cases I write a general “don’t use FTP” response, but I don’t have time to go into all the details. I’ve created this post as a place to collect all of those details, so I can reference them in other threads. IMPORTANT Apple’s official position on FTP is: All our FTP APIs have been deprecated, and you should avoid using deprecated APIs. Apple has been slowly removing FTP support from the user-facing parts of our system. The most recent example of this is that we removed the ftp command-line tool in macOS 10.13. You should avoid the FTP protocol and look to adopt more modern alternatives. The rest of this post is an informational explanation of the overall FTP picture. This post is locked so I can keep it focused. If you have questions or comments, please do create a new thread in the App & System Services > Networking subtopic and I’ll respond there. Don’t Use FTP FTP is a very old and very crufty protocol. Certain things that seem obvious to us now — like being able to create a GUI client that reliably shows a directory listing in a platform-independent manner — aren’t possible to do in FTP. However, by far the biggest problem with FTP is that it provides no security [1]. Specifically, the FTP protocol: Provides no on-the-wire privacy, so anyone can see the data you transfer Provides no client-authenticates-server authentication, so you have no idea whether you’re talking to the right server Provides no data integrity, allowing an attacker to munge your data in transit Transfers user names and passwords in the clear Using FTP for anonymous downloads may be acceptable (see the explanation below) but most other uses of FTP are completely inappropriate for the modern Internet. IMPORTANT You should only use FTP for anonymous downloads if you have an independent way to check the integrity of the data you’ve downloaded. For example, if you’re downloading a software update, you could use code signing to check its integrity. If you don’t check the integrity of the data you’ve downloaded, an attacker could substitute a malicious download instead. This would be especially bad in, say, the software update case. These fundamental problems with the FTP protocol mean that it’s not a priority for Apple. This is reflected in the available APIs, which is the subject of the next section. FTP APIs Apple provides two FTP APIs: All Apple platforms provide FTP downloads via URLSession. Most Apple platforms (everything except watchOS) support CFFTPStream, which allows for directory listings, downloads, uploads, and directory creation. All of these FTP APIs are now deprecated: URLSession was deprecated for the purposes of FTP in the 2022 SDKs (macOS 13, iOS 16, iPadOS 16, tvOS 16, watchOS 9) [2]. CFFTPStream was deprecated in the 2016 SDKs (macOS 10.11, iOS 9, iPadOS 9, tvOS 9). CFFTPStream still works about as well as it ever did, which is not particularly well. Specifically: There is at least one known crashing bug (r. 35745763), albeit one that occurs quite infrequently. There are clear implementation limitations — like the fact that CFFTPCreateParsedResourceListing assumes a MacRoman text encoding (r. 7420589) — that won’t be fixed. If you’re looking for an example of how to use these APIs, check out SimpleFTPSample. Note This sample hasn’t been updated since 2013 and is unlikely to ever be updated given Apple’s position on FTP. The FTP support in URLSession has significant limitations: It only supports FTP downloads; there’s no support for uploads or any other FTP operations. It doesn’t support resumable FTP downloads [3]. It doesn’t work in background sessions. That prevents it from running FTP downloads in the background on iOS. It’s only supported in classic loading mode. See the usesClassicLoadingMode property and the doc comments in <Foundation/NSURLSession.h>. If Apple’s FTP APIs are insufficient for your needs, you’ll need to write or acquire your own FTP library. Before you do that, however, consider switching to an alternative protocol. After all, if you’re going to go to the trouble of importing a large FTP library into your code base, you might as well import a library for a better protocol. The next section discusses some options in this space. Alternative Protocols There are numerous better alternatives to FTP: HTTPS is by far the best alternative to FTP, offering good security, good APIs on Apple platforms, good server support, and good network compatibility. Implementing traditional FTP operations over HTTPS can be a bit tricky. One possible way forward is to enable DAV extensions on the server. FTPS is FTP over TLS (aka SSL). While FTPS adds security to the protocol, which is very important, it still inherits many of FTP’s other problems. Personally I try to avoid this protocol. SFTP is a file transfer protocol that’s completely unrelated to FTP. It runs over SSH, making it a great alternative in many of the ad hoc setups that traditionally use FTP. Apple doesn’t have an API for either FTPS or SFTP, although on macOS you may be able to make some headway by invoking the sftp command-line tool. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" [1] In another thread someone asked me about FTP’s other problems, those not related to security, so let’s talk about that. One of FTP’s implicit design goals was to provide cross-platform support that exposes the target platform. You can think of FTP as being kinda like telnet. When you telnet from Unix to VMS, it doesn’t aim to abstract away VMS commands, so that you can type Unix commands at the VMS prompt. Rather, you’re expected to run VMS commands. FTP is (a bit) like that. This choice made sense back when the FTP protocol was invented. Folks were expecting to use FTP via a command-line client, so there was a human in the loop. If they ran a command and it produced VMS-like output, that was fine because they knew that they were FTPing into a VMS machine. However, most users today are using GUI clients, and this design choice makes it very hard to create a general GUI client for FTP. Let’s consider the simple problem of getting the contents of a directory. When you send an FTP LIST command, the server would historically run the platform native directory list command and pipe the results back to you. To create a GUI client you have to parse that data to extract the file names. Doing that is a serious challenge. Indeed, just the first step, working out the text encoding, is a challenge. Many FTP servers use UTF-8, but some use ISO-Latin-1, some use other standard encodings, some use Windows code pages, and so on. I say “historically” above because there have been various efforts to standardise this stuff, both in the RFCs and in individual server implementations. However, if you’re building a general client you can’t rely on these efforts. After all, the reason why folks continue to use FTP is because of it widespread support. [2] To quote the macOS 13 Ventura Release Notes: FTP is deprecated for URLSession and related APIs. Please adopt modern secure networking protocols such as HTTPS. (92623659) [3] Although you can implement resumable downloads using the lower-level CFFTPStream API, courtesy of the kCFStreamPropertyFTPFileTransferOffset property. Revision History 2025-10-06 Explained that URLSession only supports FTP in classic loading mode. Made other minor editorial changes. 2024-04-15 Added a footnote about FTP’s other problems. Made other minor editorial changes. 2022-08-09 Noted that the FTP support in URLSession is now deprecated. Made other minor editorial changes. 2021-04-06 Fixed the formatting. Fixed some links. 2018-02-23 First posted.