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

Networking Documentation

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Using activeOperationalDataSet with Matter chip-tool
I am trying to commission an ESP32-H2 Matter device using the chip-tool. It's running the Light Switch sample. I can commissioning it using the iOS Home App, so I know the code on it's working okay. I would like to understand more about the Fabric process, so I'd like to use the Home Pod powered Thread network rather than setting up an instance of Open Thread Border Router. I have created a simple iOS app and can fetch the activeOperationalDataSet from the Preferred network using func obtainPreferredNetworkCredentials() async -> (Void) { let client = THClient() let bIsPreferredAvailable = await client.isPreferredAvailable() if bIsPreferredAvailable == true { var credential: THCredentials? do { credential = try await client.preferredCredentials() if let dataset = credential?.activeOperationalDataSet { print(dataset.hexDescription) } } catch { print("Failed to get the credentials") } } } The hexDescription comes from this extension extension Data { var hexDescription: String { return reduce("") {$0 + String(format: "%02x", $1)} } } I am decoding the Data and displaying it as a hex string. It looks something like this: 0e080000000000000000000300001935060004001fffc002089f651677026f48070708fd9f65167702000ee90914b5d1097de9bb0818dc94690c0402a0f7f8 However, when I attempt to commission the device, it fails during ThreadSetup. Googling the issue says most likely the Operational Dataset is wrong in some way. Before I spend too much time on this, I want to make sure I'm doing the right thing in terms of getting the Operational Dataset to use with the chip-tool. Any help is appreciated!
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Mar ’25
Unable to recover after URLSession encounters the SSL error -9816
For years our iOS apps have experienced a networking problem, which blocks them connecting to our servers via their API endpoint domains. How can we recover after the scenario described below? Using 3rd party error logging solutions, which have different endpoint domains, we can record the error: NSUnderlyingError": Error Domain=kCFErrorDomainCFNetwork Code=-1200 "(null)" UserInfo={_kCFStreamPropertySSLClientCertificateState=0, _kCFNetworkCFStreamSSLErrorOriginalValue=-9816, _kCFStreamErrorDomainKey=3, _kCFStreamErrorCodeKey=-9816, _NSURLErrorNWPathKey=satisfied (Path is satisfied), viable, interface: pdp_ip0[lte], ipv4, dns, expensive, uses cell}, "_NSURLErrorFailingURLSessionTaskErrorKey": LocalDataTask <DEDBFA4D-810D-4438-A6A0-95E3B9668B9E>.<308>, "_kCFStreamErrorDomainKey": 3, "_NSURLErrorRelatedURLSessionTaskErrorKey": <__NSSingleObjectArrayI 0x301f82e60>( LocalDataTask <DEDBFA4D-810D-4438-A6A0-95E3B9668B9E>.<308> ) "NSLocalizedDescription": An SSL error has occurred and a secure connection to the server cannot be made., "NSLocalizedRecoverySuggestion": Would you like to connect to the server anyway? -9816 is the "server closed session with no notification" error based on comments in CoreFoundation source files. Subsequent API endpoint calls to the same domain return the same error. The SSL error occurs most prevalently after a server outage. However, despite our best efforts, we have been unable to replicate triggering the problem for development purposes via experiments with our server. When the error occurs the users report that: Fully closing (i.e. not just sending to background) and reopening the app does NOT clear connectivity to our server being blocked. Problem seems more prevalent when using mobile/cell data. Switching from mobile/cell data to WIFI resolves the connection problem and then switching back to mobile/cell data shows the problem again. So the underlying problem is not cleared. All other apps on the same device and mobile/cell data or WIFI connection, like Safari, have no problems connecting to the Internet. Deleting and reinstalling, or updating (when an update is available) resolves the problem. Or after waiting a few days the problem seems to resolve itself. The last two point above suggest that something is persisted/cached in the app preventing it from connecting properly with subsequent network attempts. Notes: We have one shared instance of the URLSession in the app for its networking because we are aware of the perils of multiple URLSession instances. We recently added conditions to call the URLSession await reset() method when detecting the SLL errors before repeating the request. It is debatable whether this reduces the problem as we still see logged cases with the subsequent requests hitting the same -9816 error. URLSession configuration: let config = URLSessionConfiguration.default config.timeoutIntervalForResource = 22 config.timeoutIntervalForRequest = 20 config.requestCachePolicy = .reloadIgnoringLocalCacheData config.urlCache = nil
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1.6k
Mar ’25
Clarification on wildcard matching of domains in NEDNSSettings - matchDomains
I have an NEPacketTunnelProvider that's configured using NEPacketTunnelNetworkSettings. I'm using NEDNSSettings to configure the DNS resolver of the packet tunnel, and would like to specify the exact domains that should use this resolver using the matchDomains member variable. While it's not explicitly mentioned in the documentation [1], I've noticed that if a domain is present in matchDomains, then all subdomains of it will also be resolved using this resolver, as if a wildcard match rule is in place. I wanted to ask if this the intended behavior, and if so, is there any way to disable it so that only exact domain matches will be resolved? I.e., if "example.com" is in the matchDomains list, I would like requests for this domain be resolved using the configured DNS resolver, while ignoring requests to the subdomain"test.example.com". [1] https://developer.apple.com/documentation/networkextension/nednssettings/matchdomains
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Mar ’25
Inquiry Regarding Differences in Wi-Fi Authentication and Encryption Between iPhone 16 Series and Other iOS 18.3 Devices
I am trying to connect an iPhone 16 (iOS 18.3) to a Wi-Fi device with the SSID "DIRECT-DR_6930_KP201128", but every time, without being able to enter the Wi-Fi password, the message "Unable to join the network 'DIRECT-DR_6930_KP201128'" is displayed. Below are the system logs from the connection failure. Could you please tell me the cause of the connection failure? By the way, an iPhone SE 2nd (iOS 18.2.1) can connect to the same Wi-Fi device without any issues. System Logs: ・Jan 31 19:18:14 900-iPhone-16-docomo Preferences(WiFiKit)[351] : {ASSOC-} association finished for DIRECT-DR_6930_KP201128 - success 0 ・Jan 31 19:18:14 900-iPhone-16-docomo runningboardd(RunningBoard)[33] : Assertion 33-351-4412 (target:[app<com.apple.Preferences(DE1AB487-615D-473C-A8D6-EAEF07337B18)>:351]) will be created as inactive as start-time-defining assertions exist ・Jan 31 19:18:14 900-iPhone-16-docomo Preferences(WiFiKit)[351] : association failure: (error Error Domain=com.apple.wifikit.error Code=12 "Unknown Error" UserInfo={NSDebugDescription=Unknown Error, NSUnderlyingError=0x303307660 {Error Domain=com.apple.corewifi.error.wifid Code=-3938 "(null)"}}) ・Jan 31 19:18:14 900-iPhone-16-docomo Preferences(WiFiKit)[351] : dismissing credentials view controller for DIRECT-DR_6930_KP201128
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Mar ’25
Auto connect 802.1x network using the selected profile in terminal or by code
Hello. I'm developing on a cross-platform app to help user connect enterprise network and found it difficult in macOS. The issue is, I guided user to install profile, but the authentication won't start immediately even the cable is plugged in or the WLAN is connected. There is still some manual operation to be done: Ethernet: Select the correct profile, and click the Connect button. Wlan: Click the Connect button. (The profile contains SSID so need't select the correct profile) Obviously, the operation is still not easy for users to understand and follow. So, is there any method to auto connect 802.1x network using the selected profile in terminal or by code? I mean, the manual operation is not necessary, maybe you can tell me a better solution. BTW, I found it possible to connect WLAN and auto select the correct profile by using this command networksetup -setairportnetwork en1 MY_SSID, but it could be very slow since the authentication seemed start 30 sec after connecting the SSID. So I believe it not the best solution.
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Mar ’25
Crash in connection loader from CFNetwork with stack traces referring to internal Apple SDKs
We found there is a significant crash reports (most of them are from iOS 17, the rest are iOS 16 and 15) comes from network loader from CFNetwork. Apparently it seems there are two types of crashes if we checked from the stack trace, the one we found from both Xcode organizer and 3rd party crash reporter is referring to URLConnectionLoader::loadWithWhatToDo and the other one from our 3rd party crash reporter (didn’t found the report from Xcode organizer) referring to _CFURLResponseCreateFromArchiveList (this one only happened on iOS 17.5 and later devices). It seems that they are both kinda similar which might point to the same root cause. From what I’ve seen, we never touch the lower level API directly, we usually use the URLSession to manage our API request. The crashed stack trace also didn’t give any indication about which of our app code that triggered the crash, it only shows calls to Apple’s internal SDKs so we are unsure how to approach this issue meanwhile the crash event already reached 800+ in the last 30 days. Unfortunately, we cannot reproduce the issue as the stack trace itself seems unclear to us. I have submitted a report through feedback assistant with number: FB14679252. Would appreciate if anyone can give any advice on what we can do to avoid this in the future and probably any hint on why it could happened. Hereby I attached the crash reports that we found each from Xcode crash report and our 3rd party crash reporter (the report said it crashed on com.apple.CFNetwork.LoaderQ) so you could get a glimpse of the similarity. Xcode crash report xcode crash report.crash 3rd party crash report 3rd party crash report.txt
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1.6k
Mar ’25
UDP Broadcast/Multicast Reception Stops for Intervals
Our app receives real-time GPS and aircraft data from devices via UDP broadcast and/or multicast on a WiFi network created by the device. We have identified that the iPhone or iPad will just stop receiving UDP broadcast/multicast data for an interval of time. In general, it appears after roughly every 128KB of data is received. In the attached screenshot from Xcode instruments, you can see the data reception alternating on/off. We have verified with Wireshark that the data is still flowing during that entire time period. And by tracking bytes received the app ultimately receives about 55% of the bytes, which tracks with the Network graph. We have used different approaches to the network code, including GCDAsyncUdpSocket, BSD Sockets, and the Network framework. We've tried it on background threads and the main thread. Tested it on iPads and iPhones. All produce the same result. The data is just never reaching the app code. Any insight on what may be temporarily disabling data reception?
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Mar ’25
Content filter stuck waiting for user
When our content filter is deployed, some customers report issues which show that the content filter activation was performed but the filter is showing the state [activated waiting for user]. This typically happens if the customer isn't deploying a profile to pre-authorise the system extension. The customers report that there was no popup shown for them to allow the filter to complete activation. Once the filter is in this state, there doesn't seem to be a way to clear it without resorting to disabling SIP. Attempting a deactivation does not work, the filter remains in the same state. Is there a way we can we resolve this "stuck" state when it happens without disabling SIP?
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Mar ’25
QUIC certificate question
I'm working on two Swift applications which are using QUIC in Network.framework for communication, one serve as the listener (server) and the other serve as the client so that they can exchange data, both the server and the client app are running under the same LAN, the problem I met is that when client try to connect to the server, the connection will fail due to boring SSL, couple questions: Since both the server app and client app are running under the same LAN, do they need TLS certificate? If it does, will self-signed certificate P12 work? I might distribute the app in App Store or in signed/notarized dmg or pkg to our users. If I need a public certificate and self signed wouldn't work, since they are just pair of apps w/o fixed dns domain etc, Is there any public certificate only for standalone application, not for the fixed web domain?
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Mar ’25
How to test application using Thread networking on MacOS?
I would like to test running some Thread Networking code on my MacOS machine: import ThreadNetwork let client = THClient() let bIsPreferredAvailable = await client.isPreferredAvailable() but I get some errors when trying to create an instance of the THClient class: Client: -[THClient connectToXPCService]_block_invoke - CTCS XPC Client is interrupted. Client: -[THClient getConnectionEntitlementValidity]_block_invoke - clientProxyWithErrorHandler Error: Error Domain=NSCocoaErrorDomain Code=4097 "connection to service named com.apple.ThreadNetwork.xpc" UserInfo={NSDebugDescription=connection to service named com.apple.ThreadNetwork.xpc} Client: -[THClient init] - XPC Client Init Failed Invalidating XPC connection. Client: -[THClient getConnectionEntitlementValidity]_block_invoke - clientProxyWithErrorHandler Error: Error Domain=NSCocoaErrorDomain Code=4097 "connection to service named com.apple.ThreadNetwork.xpc" UserInfo={NSDebugDescription=connection to service named com.apple.ThreadNetwork.xpc} How can I get the code to run?
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Mar ’25
Investigating CFNetwork Crashes on Older macOS Versions
CFNetwork None CFURLResponseGetRecommendedCachePolicy None 0 CFNetwork None CFHTTPCookieStorageUnscheduleFromRunLoop None 0 CFNetwork None /_/_CFNetworkAgentMessageProcessorMain None 0 CFNetwork None CFURLDownloadCancel None 0 CFNetwork None CFURLDownloadCancel None 0 libdispatch.dylib None /_dispatch/_block/_async/_invoke2 None We've observed intermittent crashes in our production environment, exclusively affecting customers running macOS 10.15 and 11. The crash logs consistently show a stack trace involving CFHTTPCookieStorageUnscheduleFromRunLoop and CFURLDownloadCancel within the CFNetwork framework. This suggests potential issues with cookie storage management and/or URL download cancellation. Could the team please analyze these crash logs and provide insights into: The root cause of the crashes. Potential race conditions or synchronization issues. Recommendations for mitigating or resolving the problem. Your assistance in resolving this issue is greatly appreciated."
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Mar ’25
After creating the profile using eapolcfg and attempting to connect to the enterprise network, eapolclient connection fails.
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
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Mar ’25
BSD socket APIs and macOS entitlements
I am looking for inputs to better understand MacOS entitlements. I ask this in context of OpenJDK project, which builds and ships the JDK. The build process makes uses of make tool and thus doesn't involving building through the XCode product. The JDK itself is a Java language platform providing applications a set of standard APIs. The implementation of these standard APIs internally involves calling platform specific native library functions. In this discussion, I would like to focus on the networking functions that the implementation uses. Almost all of these networking functions and syscalls that the internal implementation uses are BSD socket related. Imagine calls to socket(), connect(), getsockopt(), setsockopt(), getaddrinfo(), sendto(), listen(), accept() and several such. The JDK that's built through make is then packaged and made available for installation. The packaging itself varies, but for this discussion, I'll focus on the .tar.gz archived packaging. Within this archive there are several executables (for example: java, javac and others) and several libraries. My understanding, based on what I have read of MacOS entitlements is that, the entitlements are set on the executable and any libraries that would be loaded and used by that executable will be evaluated against the entitlements of the executable (please correct me if I misunderstand). Reading through the list of entitlements noted here https://developer.apple.com/documentation/bundleresources/entitlements, the relevant entitlements that an executable (like "java") which internally invokes BSD socket related syscalls and library functions, appear to be: com.apple.security.network.client - https://developer.apple.com/documentation/bundleresources/entitlements/com.apple.security.network.client com.apple.security.network.server - https://developer.apple.com/documentation/bundleresources/entitlements/com.apple.security.network.server com.apple.developer.networking.multicast - https://developer.apple.com/documentation/bundleresources/entitlements/com.apple.developer.networking.multicast Is my understanding correct that these are the relevant ones for MacOS? Are there any more entitlements that are of interest? Would it then mean that the executables (java for example) would have to enroll for these entitlements to be allowed to invoke those functions at runtime? Reading through https://developer.apple.com/documentation/bundleresources/entitlements, I believe that even when an executable is configured with these entitlements, when the application is running if that executable makes use of any operations for which it has an entitlement, the user is still prompted (through a UI notification) whether or not to allow the operation. Did I understand it right? The part that isn't clear from that documentation is, if the executable hasn't been configured with a relevant entitlement, what happens when the executable invokes on such operation. Will the user see a UI notification asking permission to allow the operation (just like if an entitlement was configured)? Or does that operation just fail in some behind the scenes way? Coming back to the networking specific entitlements, I found a couple of places in the MacOS documentation where it is claimed that the com.apple.developer.networking.multicast entitlement is only applicable on iOS. In fact, the entitlement definition page for it https://developer.apple.com/documentation/bundleresources/entitlements/com.apple.developer.networking.multicast says: "Your app must have this entitlement to send or receive IP multicast or broadcast on iOS. It also allows your app to browse and advertise arbitrary Bonjour service types." Yet, that same page, a few lines above, shows "macOS 10.0+". So, is com.apple.developer.networking.multicast entitlement necessary for an executable running on MacOS which deals with multicasting using BSD sockets? As a more general comment about the documentation, I see that the main entitlements page here https://developer.apple.com/documentation/bundleresources/entitlements categorizes some of these entitlements under specific categories, for example, notice how some entitlements are categorized under "App Clips". I think it would be useful if there was a category for "BSD sockets" and under that it would list all relevant entitlements that are applicable, even if it means repeating the entitlement names across different categories. I think that will make it easier to identify the relevant entitlements. Finally, more as a long term question, how does one watch or keep track of these required entitlements for these operations. What I mean is, is it expected that application developers keep visiting the macos documentation, like these pages, to know that a new entitlement is now required in a new macos (update) release? Or are there other ways to keep track of it? For example, if a newer macos requires a new entitlement, then when (an already built) executable is run on that version of macos, perhaps generate a notification or some kind of explicit error which makes it clear what entitlement is missing? I have read through https://developer.apple.com/documentation/bundleresources/diagnosing-issues-with-entitlements but that page focuses on identifying such issues when a executable is being built and doesn't explain the case where an executable has already been shipped with X entitlements and a new Y entitlement is now required to run on a newer version of macos.
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Mar ’25
iOS Not Sending DHCP Request After Quick WiFi Reconnect
I'm facing an issue where if a WiFi network is turned off and back on within a short time frame (2-4 seconds), iOS still shows the device as connected but does not send a new DHCP request. This causes a problem for my network device, which relies on the DHCP request to assign an IP address. Without the request, the device is unable to establish a socket connection properly. Is there any way to force iOS to send a DHCP request immediately when reconnecting to the network in this scenario? Are there any known workarounds or configurations that might help ensure the DHCP process is re-triggered? Any insights would be appreciated. Thanks!
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Mar ’25
Lack of parameter check for getsockopt()
I was trying to call getsockopt(fd, SOL_LOCAL, LOCAL_PEERCRED, ...), and by mistake passed a wrong value for the second parameter where it should be SOL_LOCAL. But the call still succeeded. Then I did more experiments and passed more random values for the second parameter, all succeeded. It seems there is a lack of parameter check in the implementation of getsockopt() , where it should return errors if people pass invalid parameters instead of succeeding silently. Hope the Apple engineers can help to validate and fix it.
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Mar ’25
Technical Inquiry about CoreBluetooth Scanning & NEHotspotConfigurationManager Workflow
I am writing to seek clarification on two technical issues related to iOS frameworks (CoreBluetooth and NetworkExtension). These observations are critical for optimizing our app's performance, and I would appreciate any official guidance or documentation references. CoreBluetooth Scanning Frequency and Cycle Issue: We noticed inconsistent BLE device discovery times (ranging from 0.5s to 1.5s) despite the peripheral advertising at 2Hz (500ms interval). Questions: Does iOS regulate the BLE scan interval or duty cycle internally? If yes, what factors affect this behavior (e.g., foreground/background state, connected devices)? Are there recommended practices to reduce discovery latency for peripherals with fixed advertising intervals? Is there a way to configure scan parameters (e.g., scan window/interval) programmatically, similar to Android's BluetoothLeScanner? Test Context: Device: iPhone 13 mini (iOS 17.6.1) Code: CBCentralManager.scanForPeripherals(withServices: nil, options: [CBCentralManagerScanOptionAllowDuplicatesKey: true]) NEHotspotConfigurationManager Workflow and Latency Issue: Using NEHotspotConfigurationManager.shared.apply(_:) to connect to Wi-Fi occasionally takes up to 8 seconds to complete. Questions: What is the internal workflow of the apply method? Does it include user permission checks, SSID scanning, authentication, or IP assignment steps? Are there known scenarios where this method would block for extended periods (e.g., waiting for user interaction, network timeouts)? Is the latency related to system-level retries or radio coexistence with other wireless activities (e.g., Bluetooth)? Test Context: Configuration: NEHotspotConfiguration(ssid: "TestSSID") Behavior: Delay occurs even when the Wi-Fi network is in range and credentials are correct.
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Mar ’25