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Networking Documentation

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Capturing NWConnection in Receive Closure – Risk of Strong Reference Cycle?
Hi Everyone, I have a query regarding capturing an NWConnection instance inside the receive closure, which gets invoked whenever some raw bytes are received. I want to know whether this will create a strong retain cycle or not. My understanding is that NWConnection holds a reference to the closure, and if I capture the NWConnection instance inside the closure, the closure will have a reference back to the connection, which, according to my understanding, creates a strong reference cycle. Is my understanding correct? If so, how can we break the strong reference cycle — using a capture list, or is there any other way as well? Thanks
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100
Oct ’25
Add VPN Configuration dialog
We have a VPN application and we were required by the review team to change the text in the "Add VPN Configuration" dialog due to guideline 5.4.0 Legal: VPN Apps: make it clear to the user what data is being collected and how it will be used in the permission request. It appears that showing that information in the view preceding the VPN configuration adding attempt is no longer enough. However we haven't found any changes in the API allowing to change the text in the mentioned dialog. Is there a technical possibility to change the text in the add VPN configuration dialog? Thank you
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88
Oct ’25
[iOS 26] Unable to start TLS handshake connection to devices with self-signed certificates
Hi there, We are facing some issues regarding TLS connectivity: Starting with iOS 26, the operating system refuses to open TLS sockets to local devices with self-signed certificates over Wi-Fi. In this situation, connection is no longer possible, even if the device is detected on the network with Bonjour. We have not found a workaround for this problem. We've tryied those solutions without success: Added the 'NSAppTransportSecurity' key to the info.plist file, testing all its items, such as "NSAllowsLocalNetworking", "NSExceptionDomains", etc. Various code changes to use properties such as "sec_protocol_options_set_local_identity" and "sec_protocol_options_set_tls_server_name" to no avail. Brutally import the certificate files into the project and load them via, for example, "Bundle.main.url(forResource: "nice_INTERFACE_server_cert", withExtension: "crt")", using methods such as sec_trust_copy_ref and SecCertificateCopyData. Download the .pem or .crt files to the iPhone, install them (now visible under "VPN & Device Management"), and then flag them as trusted by going to "Settings -> General -> Info -> Trust". certificates" The most critical part seems to be the line sec_protocol_options_set_verify_block(tlsOptions.securityProtocolOptions, { $2(true) }, queue) whose purpose is to bypass certificate checks and validate all of them (as apps already do). However, on iOS26, if I set a breakpoint on leg$2(true),` it never gets there, while on iOS 18, it does. I'll leave as example the part of the code that was tested the most below. Currently, on iOS26, the handler systematically falls back to .cancelled: func startConnection(host: String, port: UInt16) { self.queue = DispatchQueue(label: "socketQueue") let tlsOptions = NWProtocolTLS.Options() sec_protocol_options_set_verify_block(tlsOptions.securityProtocolOptions, { $2(true) }, queue) let parameters = NWParameters(tls: tlsOptions) self.nwConnection = NWConnection(host: .init(host), port: .init(rawValue: port)!, using: parameters) self.nwConnection.stateUpdateHandler = { [weak self] state in switch state { case .setup: break case .waiting(let error): self?.connectionDidFail(error: error) case .preparing: break case .ready: self?.didConnectSubject.onNext(Void()) case .failed(let error): self?.connectionDidFail(error: error) case .cancelled: self?.didDisconnectSubject.onNext(nil) @unknown default: break } } self.setupReceive() self.nwConnection.start(queue: queue) } These are the prints made during the procedure. The ones with the dot are from the app, while the ones without are warnings/info from Xcode: 🔵 INFO WifiNetworkManager.connect():52 - Try to connect onto the interface access point with ssid NiceProView4A9151_AP 🔵 INFO WifiNetworkManager.connect():68 - Connected to NiceProView4A9151_AP tcp_output [C13:2] flags=[R.] seq=215593821, ack=430284980, win=4096 state=CLOSED rcv_nxt=430284980, snd_una=215593821 nw_endpoint_flow_failed_with_error [C13 192.168.0.1:443 in_progress channel-flow (satisfied (Path is satisfied), viable, interface: en0[802.11], dns, uses wifi, LQM: unknown)] already failing, returning nw_connection_copy_protocol_metadata_internal_block_invoke [C13] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_protocol_metadata_internal_block_invoke [C13] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_connected_local_endpoint_block_invoke [C13] Client called nw_connection_copy_connected_local_endpoint on unconnected nw_connection nw_connection_copy_connected_remote_endpoint_block_invoke [C13] Client called nw_connection_copy_connected_remote_endpoint on unconnected nw_connection nw_connection_copy_protocol_metadata_internal_block_invoke [C14] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_protocol_metadata_internal_block_invoke [C14] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_connected_local_endpoint_block_invoke [C14] Client called nw_connection_copy_connected_local_endpoint on unconnected nw_connection nw_connection_copy_connected_remote_endpoint_block_invoke [C14] Client called nw_connection_copy_connected_remote_endpoint on unconnected nw_connection [C14 192.168.0.1:443 tcp, tls, attribution: developer] is already cancelled, ignoring cancel [C14 192.168.0.1:443 tcp, tls, attribution: developer] is already cancelled, ignoring cancel nw_connection_copy_protocol_metadata_internal_block_invoke [C15] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_protocol_metadata_internal_block_invoke [C15] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_connected_local_endpoint_block_invoke [C15] Client called nw_connection_copy_connected_local_endpoint on unconnected nw_connection nw_connection_copy_connected_remote_endpoint_block_invoke [C15] Client called nw_connection_copy_connected_remote_endpoint on unconnected nw_connection nw_connection_copy_protocol_metadata_internal_block_invoke [C16] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_protocol_metadata_internal_block_invoke [C16] Client called nw_connection_copy_protocol_metadata_internal on unconnected nw_connection nw_connection_copy_connected_local_endpoint_block_invoke [C16] Client called nw_connection_copy_connected_local_endpoint on unconnected nw_connection nw_connection_copy_connected_remote_endpoint_block_invoke [C16] Client called nw_connection_copy_connected_remote_endpoint on unconnected nw_connection [C16 192.168.0.1:443 tcp, tls, attribution: developer] is already cancelled, ignoring cancel [C16 192.168.0.1:443 tcp, tls, attribution: developer] is already cancelled, ignoring cancel 🔴 ERROR InterfaceDisconnectedViewModel.connect():51 - Sequence timeout.
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198
Oct ’25
OS 26.0 mDNSResponder suppresses DNS queries ("blocked by policy") for some devices until reboot
Hello, Since the release of iOS 26.0, we are seeing DNS traffic being blocked from within our NEPacketTunnelExtension on some devices. We have not isolated exact reproduction steps, but DNS resolves successfully for a period of time after enabling "iCloud Private Relay" (varying from 1-day to 2-weeks), until it then fails as MDNSResponder then returns: mDNSResponder [Q37046] DetermineUnicastQuerySuppression: Query suppressed for <mask.hash: 'REDACTED'> Addr (blocked by policy) DNS resolution continues to fail for all domains with the above until the device is rebooted. The Packet Tunnel intentionally does not have a DNS server set and this occurs for traffic from the Extension yet off-tunnel, which needs resolution from the system DNS server (and this configuration works perfectly for a period of time before being "blocked by policy"). The following do not resolve the issue once DNS queries are being "blocked by policy" on affected devices: disconnecting then reconnecting the vpn; toggling airplane mode for 10+ seconds; switching connection between WiFi & cellular data; disabling iCloud Private Relay. We have currently only seen this on unmanaged devices running iOS 26.0 or 26.1 beta and with iCloud Private Relay enabled. We did not see this issue on iOS 16,17 nor 18. We also have not yet seen this when iCloud Private Relay is disabled nor on iOS 26.0.1, however we cannot confirm whether they too are also affected. Is there a known a bug with iOS 26.0 & 26.1 Beta 1 that could cause this? How can we prevent DNS requests from NEPacketTunnelExtension being sporadically "blocked by policy" until the device is rebooted? Many thanks in advance.
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95
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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185
Oct ’25
NEVPNConnectionErrorDomainPlugin code 7 on URLFilter sample code
Hello, I have been playing around the the SimpleURLFilter sample code. I keep getting this error upon installed the filter profile on the device: mapError unexpected error domain NEVPNConnectionErrorDomainPlugin code 7 which then causes this error: Received filter status change: <FilterStatus: 'stopped' errorMessage: 'The operation couldn’t be completed. (NetworkExtension.NEURLFilterManager.Error error 14.)'> I can't find much info about code 7. Here is the configuration I am trying to run: <Configuration: pirServerURL: 'http://MyComputer.local:8080' pirAuthenticationToken: 'AAAA' pirPrivacyPassIssuerURL: 'http://MyComputer.local:8080' enabled: 'true' shouldFailClosed: 'true' controlProviderBundleIdentifier: 'krpaul.SimpleURLFilter.SimpleURLFilterExtension' prefilterFetchInterval: '2700.0'>
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288
Nov ’25
Example of DNS Proxy Provider Network Extension
I am trying to setup a system-wide DNS-over-TLS for iOS that can be turned off and on from within the app, and I'm struggling with the implementation details. I've searched online, searched forums here, used ChatGPT, and I'm getting conflicting information or code that is simply wrong. I can't find example code that is valid and gets me moving forward. I think I need to use NEDNSProxyProvider via the NetworkExtension. Does that sound correct? I have NetworkExtension -> DNS Proxy Capability set in both the main app and the DNSProxy extension. Also, I want to make sure this is even possible without an MDM. I see conflicting information, some saying this is opened up, but things like https://developer.apple.com/documentation/Technotes/tn3134-network-extension-provider-deployment saying a device needs to be managed. How do private DNS apps do this without MDM? From some responses in the forums it sounds like we need to parse the DNS requests that come in to the handleNewFlow function. Is there good sample code for this parsing? I saw some helpful information from Eskimo (for instance https://developer.apple.com/forums/thread/723831 ) and Matt Eaton ( https://developer.apple.com/forums/thread/665480 )but I'm still confused. So, if I have a DoT URL, is there good sample code somewhere for what startProxy, stopProxy, and handleNewFlow might look like? And valid code to call it from the main app?
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246
Oct ’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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133
Sep ’25
NWListener/NWConnection reclaimed by OS when app goes in Suspended State
I was exploring the scenarios where an NWListener or NWConnection can be invalidated or reclaimed by the OS itself. I came across the document TN2277: Networking and Multitasking, which discusses situations where iOS can reclaim the underlying socket descriptor. The document states: while the app is suspended the system may choose to reclaim resources out from underneath a network socket used by the app, thereby closing the network connection represented by that socket. From this, I understand that when the app is in a suspended state, the OS may reclaim the socket descriptor. My questions are: In what scenarios does the OS not reclaim the socket descriptor while the app is suspended, and in which cases does it reclaim it? When reclamation occurs, does the OS reclaim 'a' single NWListener/NWConnection, or does it reclaim 'all' NWListener/NWConnections opened by the application? Thanks.
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129
Sep ’25
Crash in libquic.dylib when app is backgrounded and issues an HTTP/3 request on iOS 26
Title / Summary Crash in libquic.dylib when app is backgrounded and issues an HTTP/3 request Description On iOS 26, the app crashes inside libquic.dylib while performing a network request using HTTP/3 (QUIC) after the app has moved to the background. The crash happens within low-level QUIC / libquic internals. Reproduction Steps Launch the app, perform normal operations. Background the app (press home / switch away). While in background, trigger a network request that uses HTTP/3 / QUIC. Observe that the app crashes (stack trace pointing into libquic.dylib). Expected Behavior The HTTP/3 request in background should either be handled gracefully (fail or complete) without causing a crash; the app must not be terminated due to internal libquic failures. Actual Behavior The app crashes with signals/exceptions coming from libquic.dylib (in the QUIC / packet building / encryption / key state logic) when a HTTP/3 request is made in background. Environment / Device Information • OS: iOS 26 • Device: iPhone 13 Pro Max • Network environment: (Wi-Fi / Cellular) • HTTP/3 support: enabled in URLSession / Network framework Stack Trace: 8eedc0df3d914b0faf8def9af3b21574-symbolicated.crash
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198
Sep ’25
Wi-Fi Aware Building peer-to-peer app sample app Error
We are using wifi_aware demo at https://developer.apple.com/documentation/wifiaware/building-peer-to-peer-apps. We use iPhone 16 with ios26 to install this app successfully for the first time. After then we want to remove some paired devices, but the function used to delete paired device is not founded. So we uninstall the app, and intend to install it again. This time, it jump to the interface displaying the message "This device does not support Wi-Fi Aware". We are confused by this and don't know what to do. Instead of using other devices, how can we successfully install the app on this device. The iphone, Apple computer and Xcode environment maintain the same for sure. We sincerely appreciate your reply.
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180
Sep ’25
OnDemand not applying after profile switch
We currently have a PacketTunnelProvider providing a VPN connection to managed devices. Our profile locks this down with OnDemandEnabled and OnDemandUserOverrideDisabled set to true. We've had reports of the OnDemand feature not kicking in on macOS when switching profiles or creating new profiles for managed users (but this works for the initial user login). When switching profiles, OnDemand does not enable; however, if the user manually enables the VPN and then disables, OnDemand will now correctly turn the connection back on. The installed profile contains: OnDemandEnabled: 1 OnDemandRules: Connect Action for WiFi, Cellular, and Ethernet OnDemandUserOverrideDisabled: 1 From sysdiagnose logs, I see some interesting logs for nesessionmanager: Handling a network changed event Resetting VPN On Demand Found 0 registrations for [...].PacketTunnel Failed to find [...].PacketTunnel app extension using neagent Plugin is not available in launch services Plugin is not installed (I also see some failures with LSApplicationProxy, but not sure if those are relevant.) Eventually, I see: Plugin is installed Enabling VPN On Demand And things seem to kick off more as expected from that point on. Do we have any guidance on how to address this issue? We also have a ticket submitted with Feedback Assistant.
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123
Sep ’25
Performance degradation of HTTP/3 requests in iOS app under specific network conditions
Hello Apple Support Team, We are experiencing a performance issue with HTTP/3 in our iOS application during testing. Problem Description: Network requests using HTTP/3 are significantly slower than expected. This issue occurs on both Wi-Fi and 4G networks, with both IPv4 and IPv6. The same setup worked correctly in an earlier experiment. Key Observations: The slowdown disappears when the device uses: · A personal hotspot. · Network Link Conditioner (with no limitations applied). · Internet sharing from a MacBook via USB (where traffic was also inspected with Wireshark without issues). The problem is specific to HTTP/3 and does not occur with HTTP/2. The issue is reproducible on iOS 15, 18.7, and the latest iOS 26 beta. HTTP/3 is confirmed to be active (via assumeHttp3Capable and Alt-Svc header). Crucially, the same backend endpoint works with normal performance on Android devices and using curl with HTTP/3 support from the same network. I've checked the CFNetwork logs in the Console but haven't found any suspicious errors or obvious clues that explain the slowdown. We are using a standard URLSession with basic configuration. Attempted to collect qlog diagnostics by setting the QUIC_LOG_DIRECTORY=~/ tmp environment variable, but the logs were not generated. Question: What could cause HTTP/3 performance to improve only when the device is connected through a hotspot, unrestricted Network Link Conditioner, or USB-tethered connection? The fact that Android and curl work correctly points to an issue specific to the iOS network stack. Are there known conditions or policies (e.g., related to network interface handling, QoS, or specific packet processing) that could lead to this behavior? Additionally, why might the qlog environment variable fail to produce logs, and are there other ways to obtain detailed HTTP/3 diagnostic information from iOS? Any guidance on further diagnostic steps or specific system logs to examine would be greatly appreciated. Thank you for your assistance.
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316
Nov ’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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137
Sep ’25
Local Hotspot
Hello, we are developing hardware that needs to connect to an iPhone via Wi-Fi to send requests to a server. On Android, we have managed to create a programmatic local hotspot within the app to facilitate connection and improve the user experience. On iOS, however, Personal Hotspot must be manually enabled from the system settings, and the user must manually enter the SSID and password, which significantly degrades the UX. My questions are: Is there a workaround, unofficial method, or private API to generate a local hotspot from an app on iOS, similar to what can be done on Android? Is there an alternative within the MFi program or through specific frameworks to facilitate a quick and automatic connection between the hardware and the iPhone without relying on the manual Personal Hotspot? Are there any best practices for improving the local Wi-Fi connection experience between an accessory and an iPhone in the absence of hotspot controls? I would appreciate any guidance, experience, or resources that would help me better understand the feasible options in iOS for scenarios where fast and direct communication between hardware and mobile devices via Wi-Fi is required.
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96
Sep ’25
SwiftSMTP broken: Error ioOnClosedChannel on latest macOS
Hi! I wrote an internal used backup command line tool which is in use since several years. Today I got an error while sending an email: “Failed: ioOnClosedChannel”. I assume that the latest macOS updates did break my app. On the server I use macOS 15.7 and on my development machine macOS 26. Here is the related code: private func sendMail() { var a : [Email.Attachment] = [] if self.imageData != nil { switch self.imageType { case .tiff: a.append(Email.Attachment(name: "Statistics.tif", contentType: #"image/tiff"#, contents: ByteBuffer(bytes: self.imageData!))) case .pdf: a.append(Email.Attachment(name: "Statistics.pdf", contentType: #"application/pdf"#, contents: ByteBuffer(bytes: self.imageData!))) case .unknown: fatalError("Unimplemented attachment type!") } } mailHtml = mailHtml.replacingOccurrences(of: "<br>", with: "<br>\n") let email = Email(sender: .init(name: "Backup", emailAddress: "SENDER@MYDOMAIN"), replyTo: nil, recipients: recipients, cc: [], bcc: [], subject: self.subject, body: .universal(plain: self.mailText, html: mailHtml), attachments: a) let evg = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount) let mailer = Mailer(group: evg, configuration: smtpConfig, transmissionLogger: nil) do { print("Sending mail... ", terminator: "") try mailer.send(email: email).wait() // <-- ERROR HERE Failed: ioOnClosedChannel print("done.") } catch { print("Failed: \(error)") } do { try evg.syncShutdownGracefully() } catch { print("Failed shutdown: \(error)") } } I use https://github.com/sersoft-gmbh/swift-smtp. Any clue about the reason of this error? TIA, GreatOm
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236
Sep ’25
iPhone 17(iOS26) Unable to join the Wi-Fi(TKIP)
Device: iPhone 17 Series System: iOS 26.0.0 Wi-Fi: TKIP encryption protocol Question: Unable to join the network We have several products that are used by connecting to iPhone via Wi-Fi. Recently, many customers who have purchased the iPhone 17 series have reported that they are unable to connect to Wi-Fi. For Wi-Fi with TKIP encryption, after entering the password correctly to connect to the Wi-Fi, a pop-up appears stating "Unable to join the network.". Only Wi-Fi with WPA2-AES can be used normally. Before that, during the iPhone 11 era or even earlier, the TKIP encryption method was in normal use. However, the new iPhone models were incompatible with it, which obviously caused great inconvenience. I hope the engineers can fix this issue to support Wi-Fi with older encryption protocols.
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510
3w
Too many mach ports?
We have a customer reporting a bunch of problems with our (Transparent Proxy Provider-based) suite. Looking at a sysdiagnose, I see that our GUI applet was killed: Termination Reason: Namespace PORT_SPACE, Code 14123288431434181290 (Limit 305834 ports) Exceeded system-wide per-process Port Limit Looking at the top.txt file from it, I see that it has 193,086 ports -- compared to about ~250 on one of my test systems. Has anyone run into this? Any idea what might be causing it? (I'm still poring over the sysdiagnose, but I don't see any kernel logs around that time -- except that our process does close a dozen or so ports because of cancellation.)
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208
Sep ’25
App in China is good, but app in Japan is bad, why? SSL?
Macbook OS Version: macOS 14.7.3 (23H417) Mobile OS: iOS Mobile OS Version: iOS 18.6.2 Mobile Manufacturer: Apple Mobile Model: iPhone 12 Pro Max Page Type: vue vue Version: vue2 Packaging Method: Cloud Packaging Project Creation Method: HBuilderX Steps: The backend server is deployed on AWS in Japan with a Japanese IP. Packaging the APP in HBuilderX and publishing it to the Apple App Store were both successful. In a subsequent version, we planned to add a push notification feature and selected uniPush V2. Due to the separation of frontend and backend, the frontend APP implements functions such as registration, login, password change, page content display, and product lists through the server's RESTful APIs. Test colleagues reported that the APP could not load pages when used in Japan; however, it worked normally in China. In China: Pinging the server IP and domain from a MacBook was successful. Testing the API with Postman on a MacBook was successful. In Japan: Pinging the server IP and domain from a MacBook was successful. Testing the API with Postman on a MacBook failed with the error: HandshakeException: Connection terminated during handshake This appears to be an SSL communication failure. We tested the SSL certificate using www.ssllabs.com/ssltest and received an A+ rating. The certificate should not be an issue. we deselected uniPush V2, repackaged the APP, and uploaded it to TestFlight. The result remained the same: the APP content failed to load in Japan, while it worked normally in China. Expected Result: Access to the Japanese server APIs should work normally both in China and Japan. Actual Result: The APP content fails to load when used in Japan, but works normally in China.
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192
Sep ’25