Networking

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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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SSH app
Hello. I would like to develop an application that sends SSH commands via my phone to the server. I know that applications of this type exist, but they are not suitable for my use as a blind person who uses a screen reader. I hope you can help me find libraries that will assist me in development, or ready-made, open-source projects that I can develop and modify if necessary. Thank you in advance.
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58
Mar ’25
Understanding when the push provider calls stop() with the noNetworkAvailable reason
I have 3 phones iPhone 14 iOS 18.3 iPhone Xr iOS 18.5 iPhone Xr iOS 18.4.1 My app has a network extension, and I've noticed each phone having their connectivity interupted by calls on the push provider, calling stop with the noNetworkAvailable reason. The point of confusion is that each phone seems to get it's interuption at different times. For example one will get an interuption at 1:00, while the others is fine, while at 3:00 another will get an interuption, while the others are fine. This is confusing since a "no network available" seems to imply a problem with the router, or access point, but if that were the case, one would believe it should affect all the phones on the wifi. I don't see less interuptions on the iPhone14 vs the iPhone Xr. Do you believe the iOS version is affecting the performance? Could you please give me some insight, as to what could be going on inside these phones? P.S. I also see an error pop up when using NWConnection, this is inside the App. The state update handler will sometimes return the state, waiting(POSIX(.ENETDOWN)) Is there any relation to what's going on in the extension?
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84
Jun ’25
Apple Watch Data to Server
I was wondering which is the preferred way to send a lot of data from sensors of the apple watch to server. It is preferred to send small chucks to iphone and then to server or directly send bulk data to server from watch. How does it affect battery and resources from watch ? Are there any triggers that I can use to ensure best data stream. I need to send at least once a day. Can I do it in background or do I need the user to have my app in the foreground ? Thank you in advance
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198
Jun ’25
Real-Time WatchConnectivity Sync Not Working Between iPhone and Apple Watch
Hi everyone, I'm building a health-focused iOS and watchOS app that uses WatchConnectivity to sync real-time heart rate and core body temperature data from iPhone to Apple Watch. While the HealthKit integration works correctly on the iPhone side, I'm facing persistent issues with WatchConnectivity — the data either doesn't arrive on the Watch, or session(_:didReceiveMessage:) never gets triggered. Here's the setup: On iPhone: Using WCSession.default.sendMessage(_:replyHandler:errorHandler:) to send real-time values every few seconds. On Apple Watch: Implemented WCSessionDelegate, and session(_:didReceiveMessage:) is supposed to update the UI. Both apps have WCSession.isSupported() checks, activate the session, and assign delegates correctly. The session state shows isPaired = true and isWatchAppInstalled = true. Bluetooth and Wi-Fi are on, both devices are unlocked and nearby. Despite all this, the Watch never receives messages in real-time. Sometimes, data comes through in bulk much later or not at all. I've double-checked Info.plist configurations and made sure background modes include "Uses Bluetooth LE accessories" and "Background fetch" where appropriate. I would really appreciate guidance on: Best practices for reliable, low-latency message delivery with WatchConnectivity. Debugging steps or sample code to validate message transmission and reception. Any pitfalls related to UI updates from the delegate method. Happy to share further details. Thanks in advance!
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236
Jun ’25
Securely transmit UIImage to app running on desktop website
Hello everyone, I'm trying to figure out how to transmit a UIImage (png or tiff) securely to an application running in my desktop browser (Mac or PC). The desktop application and iOS app would potentially be running on the same local network (iOS hotspot or something) or have no internet connection at all. I'm trying to securely send over an image that the running desktop app could ingest. I was thinking something like a local server securely accepting image data from an iPhone. Any suggestions ideas or where to look for more info would be greatly appreciated! Thank you for your help.
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121
May ’25
Error Domain=com.apple.wifi.apple80211API.error Code=-528342014 "tmpErr"
On my macOS 15.x device, frequently encountering the error: Error Domain=com.apple.wifi.apple80211API.error Code=-528342014 "tmpErr" when connecting to an EAP WiFi network using CWWiFiClient. Restarting the device temporarily resolves the issue, but it reoccurs after some time. What could be causing this, and how can it be resolved programmatically?
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489
Mar ’25
Network Framework: LAN vs Wifi vs Peer to Peer Wifi Switching
I would like to understand the behaviour of Network framework when I have established a connection between 2 iOS devices which are connected through LAN and the same Wifi. Assumptions: Enabled includePeerToPeer. Devices are discovered and connected through Bonjour: When the connection establishes for the first time, does it automatically decide which interface to pick? I see some posts which point to Happy Eyeball algorithm but that seem to point more towards ipv4 vs ipv6 rather than Wifi vs LAN vs P2P. In the middle of a connection, if the established connection has issues, does the Network framework automatically switch to the best available interface? If not, I would assume the app will have to handle the switching in betterPathUpdateHandler callback? I’m curious what needs to be done here. Do I just create a new connection and hope that it picks the actual better path? The NWInterface.InterfaceType doesnt have a type for peer to peer wifi. Does that mean that when the interface actually switches to peer to peer, the InterfaceType will be other? It would be great if there is a workflow or example of how this needs to be handled with multiple available Interfaces.
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97
Oct ’25
iOS reports incorrect own IP address to apps when connected to WiFi
I have an iPhone app which relies heavily on TCP/IP communication in the local network. Therefore, the application starts a server socket and accepts incoming connections. This worked flawlessly for a long time and we had no problems with this. Problem In the last days however, we observed that for some iPhones with the server role other devices cannot connect to the server of our app. The server does not accept incoming connections on the devices IP address and the client times out. Environment Both iPhones (the server and the client) are in the same network with 192.168.1.0 address range and 255.255.255.0 subnet mask. The server has the IP 192.168.1.11 and the client has 192.168.1.22. This is a normal home WiFi network with no special firewall rules. Both devices have mobile data disabled and the "access local network" permission is granted. The server socket is bound to all interfaces (0.0.0.0). More technical symptoms When the server iPhone is in this faulty state, it seems like it somehow has two ip addresses: 192.168.2.123 and 192.168.1.11 The WiFi preferences show the (correct) .1.11 ip address. The Apps however see the (wrong) .2.123 ip address. I cannot explain where the other ip address comes from and why the device thinks it has this ip address. I've collected interface diagnosis information on a faulty iPhone and it listed the following interfaces and IPs: en0 -> 192.168.2.123 lo0 -> 127.0.0.1 pdp_ip0 (cellular) -> 192.0.0.2 pdp_ip1 to pdp_ip6 (cellular) -> -/- ipsec0 to ipsec6 (vpn) -> -/- llw0 (vpn) -> -/- awdl0 -> -/- anpi0 -> -/- ap1 -> -/- XHC0 -> -/- en1 and en2 (wired) -> -/- utun0 to utun2 (vpn) -> -/- The correct ip of the device is not listed anywhere in this list. A reboot helped to temporarily fix this problem. One user reported the same issue again a few hours later after a reboot. Switching off WiFi and reconnecting does not solve the problem. This issue occurred on several iPhones with the following specs: iOS Version 18.1.1, 18.3.1 iPhone 13 Pro, iPhone 13 Pro Max, iPhone 15 Pro The problem must be on the server side as the client can successfully connect to any other device in the same network. Question(s) Where does this second IP come from and why does the server not accept connections to either ip even though it is bound to 0.0.0.0? Are there any iOS system settings which could lead to this problem? (privacy setting, vpn, ...) What could be done to permanently fix this issue?
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273
Mar ’25
WiFi 6 MIMO and spatial audio support
On "Accessory Interface Specification CarPlay Addendum R10", it says that it is recommended that the accessory uses a MIMO (2x2) hardware configuration, does this imply that WiFi 5 and SISO (1X1) will be phased out in the near future? When will WiFi 6 MIMO (2x2) become mandatory? On "Accessory Interface Specification CarPlay Addendum R10", it says that Spatial Audio is mandatory. However, for aftermarket in-vehicle infotainment (IVI) system due to the number of speakers are less than 6, is it allowed not to support spatial audio for this type of aftermarket IVI system?
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94
Jul ’25
Behavior of Pending Receive Callbacks on Canceled NWConnection (UDP) Registered to Custom Serial Dispatch Queue
Hi Everyone, I’m working on a communication system for my app using NWConnection with the UDP protocol. The connection is registered to a custom serial dispatch queue. However, I’m trying to understand what the behavior will be in a scenario where the connection is canceled while there are still pending receive operations in progress. Scenario Overview: The sender is transmitting n = 100 packets to the receiver, out of which 40 packets have already been sent (i.e., delivered to the Receiver). The receiver has posted m = 20 pending receive operations, where each receive operation is responsible for handling one packet. The receiver has already successfully processed x = 10 packets. At the time of cancellation, the receiver’s buffer still holds m = 20 packets that are pending for processing, and k = 10 pending receive callbacks are in the dispatch queue, waiting to be executed. At same time when the 10th packet was processed another thread triggers .cancel() on this accepted NWConnection (on the receiver side), I need to understand the impact on the pending receive operations and their associated callbacks. My Questions: What happens to the k = 10 pending receive callbacks that are in the dispatch queue waiting to be triggered when the connection is canceled? Will these callbacks complete successfully and process the data? Or, because the connection is canceled, will they complete with failure? What happens to the remaining pending receive operations that were initiated but have not yet been scheduled in the dispatch queue? For the pending receive operations that were already initiated (i.e., the network stack is waiting to receive the data, but the callback hasn’t been scheduled yet), will they fail immediately when the connection is canceled? Or is there any chance that the framework might still process these receives before the cancellation fully takes effect?
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326
Feb ’25
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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107
Oct ’25
Clarification on content filter limitation
I am seeking clarification regarding the capabilities and limitations of deploying content filter profiles, such as web content filters, on unsupervised iOS devices through MDM solutions. Specifically, is per-app content filtering supported on unsupervised devices, or is it restricted to supervised devices only? If such restrictions exist, are there recognized workarounds? Additionally, I would like to understand if there are specific permissions or entitlements that enable apps to perform advanced filtering or monitoring functions on unsupervised devices. Any guidance or references to official documentation would be greatly appreciated.
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68
Aug ’25
Determine outgoing flow source IPs without allowing data leakage using NEFilterDataProvider
I'm looking for help with a network extension filtering issue. Specifically, we have a subclass of NEFilterDataProvider that is used to filter flows based upon a set of rules, including source IP and destination IP. We've run into an issue where the source IP is frequently 0.0.0.0 (or the IPv6 equivalent) on outgoing flows. This has made it so rules based upon source IP don't work. This is also an issue as we report these connections, but we're lacking critical data. We were able to work around the issue somewhat by keeping a list of flows that we allow that we periodically check to see if the source IP is available, and then report after it becomes available. We also considered doing a "peekBytes" to allow a bit of data to flow and then recheck the flow, but we don't want to allow data leakage on connections that should be blocked because of the source IP. Is there a way to force the operating system or network extension frameworks to determine the source IP for an outbound flow without allowing any bytes to flow to the network? STEPS TO REPRODUCE Create a network filtering extension for filtering flows using NEFilterDataProvider See that when handleNewFlow: is called, the outgoing flow lacks the source IP (is 0.0.0.0) in most cases There is this post that is discussing a similar question, though for a slightly different reason. I imagine the answer to this and the other post will be related, at least as far as NEFilterDataProvider:handleNewFlow not having source IP is considered. Thanks!
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161
Apr ’25
Mechanism to Identify Source App for TLS Inspection in Packet Tunnel Provider on iOS
We are a Layer 3 VPN provider offering a comprehensive SASE (Secure Access Service Edge) solution that includes TLS inspection, threat protection, granular access control, and secure access to private resources. One of the key challenges we face involves TLS inspection. Many mobile applications, especially on iOS, implement certificate pinning, which causes them to fail when TLS inspection is applied. These apps expect connections to be secured with a specific certificate or trusted certificate authority, and inspection disrupts this trust model. On iOS, the current limitation is that the Packet Tunnel Provider extension does not provide visibility into the originating application (i.e., there is no API to obtain the app’s bundle ID or package name associated with a given network connection). Due to this, we are unable to dynamically determine whether TLS inspection should be bypassed for a particular app. While Apple’s Per-App VPN is one possible solution, it introduces a significant drawback: any applications that are excluded from the VPN configuration are entirely outside the VPN tunnel. This means they do not benefit from any of our SASE features — including secure access to internal resources, DNS/web content filtering, or threat detection. This limits the effectiveness of our solution in environments where both inspection and secure access are critical. We would like to understand whether iOS has any current or planned capabilities to associate a network flow (e.g., a 5-tuple: source IP, destination IP, source port, destination port, and protocol) with the originating app. Such a capability would allow us to programmatically identify certificate-pinned apps and selectively disable TLS inspection without excluding them entirely from the VPN, thereby preserving the full set of SASE protections. Is there any guidance or roadmap update from Apple that addresses this use case?
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59
Jul ’25
Can NETunnelProviderManager.protocolConfiguration be changed on the fly?
I am learning about layer 3 VPN implementations for MacOS, and am slowly making my way through docs and tutorials. I noticed that part of creating an instance of NETunnelProviderManager on the app side of the project requires the specification of protocolConfiguration via an instance of NETunnelProviderProtocol. One of the arguments for this class is serverAdress, which to my understanding, tells the OS where to route traffic towards at the end of the day. My question: many VPNs these days allow the option to specify the location for which you want your traffic to be routed through. I imagine this would necessitate changing this serverAddress field in the backend. However, setting this option (on a commercially available VPN) doesn't typically prompt the OS notification that you get when initially installing a VPN configuration for the first time. How is this functionality achieved? I could see one possible solution being that most VPN providers route through a main service beforehand (so the first IP in the chain never has to change), though I could see this being problematic for a number of other reasons. Assuming you have a valid NETunnelProviderManager object called manager, is this valid? self.manager?.protocolConfiguration?.serverAddress = "somewhereElse" Even if it compiles, will the traffic be properly re-routed? My understanding of the flow right now is that in order to "lock in" a new configuration, or modify it, you need to call manager.saveToPreferences, which triggers the OS notification I mentioned earlier.
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304
Feb ’25
NSProcessInfo hostName holds the process for 30+ seconds
We have used ::gethostname to retrieve hostname in our tunnel provider extension and found it returns "localhost" on iOS 17+. So we changed to use [[NSProcessInfo processInfo] hostName]. However it often caused 30+ delay in the extension process on a few devices and always returns "localhost". The sysdiagnose shows a lot of DNS query logs as below: default mDNSResponder 2025-03-19 17:15:12.453769 +0800 75281: 0x11ad501 [R80937] DNSServiceCreateConnection START PID[79767](ACExtension) default mDNSResponder 2025-03-19 17:15:12.453892 +0800 75281: 0x11ad501 [R80938] DNSServiceQueryRecord START -- qname: <mask.hash: 'fNnSAdyuhKXqCny8+neXvw=='>, qtype: PTR, flags: 0x15000, interface index: -1, client pid: 79767 (ACExtension), name hash: 84de01e1 default mDNSResponder 2025-03-19 17:15:12.458395 +0800 75281: 0x11ad501 [R80939] DNSServiceQueryRecord START -- qname: <mask.hash: '2X6qN/YT0yh2psKwrGWokg=='>, qtype: PTR, flags: 0x15000, interface index: 0, client pid: 79767 (ACExtension), name hash: f25c923e default mDNSResponder 2025-03-19 17:15:12.462924 +0800 75281: 0x11ad501 [R80940] DNSServiceQueryRecord START -- qname: <mask.hash: 'peyRWEblLKbNvcOXPjSeMQ=='>, qtype: PTR, flags: 0x15000, interface index: 0, client pid: 79767 (ACExtension), name hash: 83323cc4
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121
Mar ’25
Getting WIFI SSID
Greetings I'm trying to get on iPad the SSID from the wifi I'm connected to. For that, I added the wifi entitlement and I'm requesting permission to the user for Location. Once I have it, I'm using the function CNCopySupportedInterfaces to get the interfaces, but I can only receive the en0, which using the method CNCopyCurrentNetworkInfo returns nil. I also tried using the NEHotspotNetwork.fetchCurrent and the SSID keeps being nil. So right now I'm drawing a blank. Is there any way to make it work? Thanks.
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339
May ’25