General: Forums subtopic: App & System Services > Networking TN3151 Choosing the right networking API Networking Overview document — Despite the fact that this is in the archive, this is still really useful. TLS for App Developers forums post Choosing a Network Debugging Tool documentation WWDC 2019 Session 712 Advances in Networking, Part 1 — This explains the concept of constrained networking, which is Apple’s preferred solution to questions like How do I check whether I’m on Wi-Fi? TN3135 Low-level networking on watchOS TN3179 Understanding local network privacy Adapt to changing network conditions tech talk Understanding Also-Ran Connections forums post Extra-ordinary Networking forums post Foundation networking: Forums tags: Foundation, CFNetwork URL Loading System documentation — NSURLSession, or URLSession in Swift, is the recommended API for HTTP[S] on Apple platforms. Network framework: Forums tag: Network Network framework documentation — Network framework is the recommended API for TCP, UDP, and QUIC on Apple platforms. Building a custom peer-to-peer protocol sample code (aka TicTacToe) Implementing netcat with Network Framework sample code (aka nwcat) Configuring a Wi-Fi accessory to join a network sample code Moving from Multipeer Connectivity to Network Framework forums post Network Extension (including Wi-Fi on iOS): See Network Extension Resources Wi-Fi Fundamentals TN3111 iOS Wi-Fi API overview Wi-Fi Aware framework documentation Wi-Fi on macOS: Forums tag: Core WLAN Core WLAN framework documentation Wi-Fi Fundamentals Secure networking: Forums tags: Security Apple Platform Security support document Preventing Insecure Network Connections documentation — This is all about App Transport Security (ATS). Available trusted root certificates for Apple operating systems support article Requirements for trusted certificates in iOS 13 and macOS 10.15 support article About upcoming limits on trusted certificates support article Apple’s Certificate Transparency policy support article What’s new for enterprise in iOS 18 support article — This discusses new key usage requirements. Technote 2232 HTTPS Server Trust Evaluation Technote 2326 Creating Certificates for TLS Testing QA1948 HTTPS and Test Servers Miscellaneous: More network-related forums tags: 5G, QUIC, Bonjour On FTP forums post Using the Multicast Networking Additional Capability forums post Investigating Network Latency Problems forums post WirelessInsights framework documentation iOS Network Signal Strength Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com"

I've had a Unreal Engine project that uses libwebsocket to make a websocket connection with SSL to a server. Recently I made a build using Unreal Engine 5.4.4 on MacOS Sequoia 15.5 and XCode 16.4 and for some reason the websocket connection now fails because it can't get the local issuer certificate. It fails to access the root certificate store on my device (Even though, running the project in the Unreal Editor works fine, it's only when making a packaged build with XCode that it breaks) I am not sure why this is suddenly happening now. If I run it in the Unreal editor on my macOS it works fine and connects. But when I make a packaged build which uses XCode to build, it can't get the local issuer certificate. I tried different code signing options, such as sign to run locally or just using sign automatically with a valid team, but I'm not sure if code signing is the cause of this issue or not. This app is only for development and not meant to be published, so that's why I had been using sign to run locally, and that used to work fine but not anymore. Any guidance would be appreciated, also any information on what may have changed that now causes this certificate issue to happen. I know Apple made changes and has made notarizing MacOS apps mandatory, but I'm not sure if that also means a non-notarized app will now no longer have access to the root certificate store of a device, in my research I haven't found anything about that specifically, but I'm wondering if any Apple engineers might know something about this that hasn't been put out publicly.

Hello, I understand that to discover and pair a device or accessory with Wi-Fi Aware, we can use either the DeviceDiscoveryUI or AccessorySetupKitUI frameworks. During the pairing process, both frameworks prompt the user to enter a pairing code. Is this step mandatory? What alternatives exist for devices or accessories that don't have a way to communicate a pairing code to the user (for example, devices or accessories without a display or voice capability)? Best regards, Gishan

Getting -10985 error from urlSession while attempting to make a connection. Not sure why this is happening if anyone is aware please help

My app attempts to upload events and logging data when the user backgrounds the app (i.e., when applicationDidEnterBackground is triggered) by creating an uploadTask using a URLSession with a URLSessionConfiguration.background. When uploading these events after being backgrounded, we call beginBackgroundTask on UIApplication, which gives us about 25-30 seconds before the expirationHandler gets triggered. I am noticing, however, that the expirationHandler is frequently called and no upload attempts have even started. This might be reasonable if, for example, I had other uploads in progress initiated prior to backgrounding, but this is not the case. Could someone confirm that, when initiating an uploadTask while the app is backgrounded using a backgroundSession, there's really no way to predict when that upload is going to begin? My observation is that about 10-20% of the time it does not begin within 20 seconds of backgrounding, and I have many events coming from clients in the field showing as much.

Network.framework: Happy Eyeballs cancels also-ran only after WebSocket handshake (duplicate WS sessions) Hi everyone 👋 When using NWConnection with NWProtocolWebSocket, I’ve noticed that Happy Eyeballs cancels the losing connection only after the WebSocket handshake completes on the winning path. As a result, both IPv4 and IPv6 attempts can send the GET / Upgrade request in parallel, which may cause duplicate WebSocket sessions on the server. Standards context RFC 8305 §6 (Happy Eyeballs v2) states: Once one of the connection attempts succeeds (generally when the TCP handshake completes), all other connections attempts that have not yet succeeded SHOULD be canceled. This “SHOULD” is intentionally non-mandatory — implementations may reasonably delay cancellation to account for additional factors (e.g. TLS success or ALPN negotiation). So Network.framework’s current behavior — canceling after the WebSocket handshake — is technically valid, but it can have practical side effects at the application layer. Why this matters WebSocket upgrades are semantically HTTP GET requests (RFC 6455 §4.1). Per RFC 9110 §9.2, GET requests are expected to be safe and idempotent — they should not have side effects on the server. In practice, though, WebSocket upgrades often: include Authorization headers or cookies create authenticated or persistent sessions So if both IPv4 and IPv6 paths reach the upgrade stage, the server may create duplicate sessions before one connection is canceled. Questions / Request Is there a way to make Happy Eyeballs cancel the losing path earlier — for example, right after TCP or TLS handshake — when using NWProtocolWebSocket? If not, could Apple consider adding an option (e.g. in NWProtocolWebSocket.Options) to control the cancellation threshold, such as: after TCP handshake after TLS handshake after protocol handshake (current behavior) That would align the implementation more closely with RFC 8305 and help prevent duplicate, non-idempotent upgrade requests. Context I’m aware of Quinn’s post Understanding Also-Ran Connections. This report focuses specifically on the cancellation timing for NWProtocolWebSocket and the impact of duplicate upgrade requests. Although RFC 6455 and RFC 9110 define WebSocket upgrades as safe and idempotent HTTP GETs, in practice they often establish authenticated or stateful sessions. Thus, delaying cancellation until after the upgrade can create duplicate sessions — even though the behavior is technically RFC-compliant. Happy to share a sysdiagnose and sample project via Feedback if helpful. Thanks! 🙏 Example log output With Network Link Conditioner (Edge): log stream --info --predicate 'subsystem == "com.apple.network" && process == "WS happy eyeballs"' 2025-11-03 17:02:48.875258 [C3] create connection to wss://echo.websocket.org:443 2025-11-03 17:02:48.878949 [C3.1] starting child endpoint 2a09:8280:1::37:b5c3:443 # IPv6 2025-11-03 17:02:48.990206 [C3.1] starting child endpoint 66.241.124.119:443 # IPv4 2025-11-03 17:03:00.251928 [C3.1.1] Socket received CONNECTED event # IPv6 TCP up 2025-11-03 17:03:00.515837 [C3.1.2] Socket received CONNECTED event # IPv4 TCP up 2025-11-03 17:03:04.543651 [C3.1.1] Output protocol connected (WebSocket) # WS ready on IPv6 2025-11-03 17:03:04.544390 [C3.1.2] nw_endpoint_handler_cancel # cancel IPv4 path 2025-11-03 17:03:04.544913 [C3.1.2] TLS warning: close_notify # graceful close IPv4

On my iPhone 16 Pro and iPhone 16 Pro Max devices, running iOS 26.0, 26.0.1, and 26.1, Wi-Fi raw socket communication works flawlessly. Even after keeping the connection active for over 40 minutes, there are no disconnections during data transmission. However, on the iPhone 17 and iPhone 17 Pro, the raw socket connection drops within 20 seconds. Once it disconnects, the socket cannot reconnect unless the Wi-Fi module itself is reset. I believe this issue is caused by a bug in the iPhone 17 series’ communication module. I have looked into many cases, and it appears to be related to a bug in the N1 chipset. Are there any possible solutions or workarounds for this issue?

I am trying to communicate with the backend of my project. So I need to install the certificate into the simulator. I have the .pem file but when I drag-dropped it into the simulator, I got the error "Simulator device failed to complete the requested operation.". The simulator is an iPhone 16 Pro running iOS 18.5. Is there any way to install the cert to my simulator? PS: I can't use Apple Configurator or MDM because I am using the office's Mac. And I can't install anything there. So I can only do it manually.

My application (using a nested framework for networking) was working correctly on iPadOS 18, but failed to perform a UDP broadcast operation after upgrading the device to iPadOS 26. The low-level console logs consistently show a "Permission denied" error. Symptoms & Error Message: When attempting to send a UDP broadcast packet using NWConnection (or a similar low-level socket call within the framework), the connection fails immediately with the following error logged in the console: nw_socket_service_writes_block_invoke [C2:1] sendmsg(fd 6, 124 bytes) [13: Permission denied] (Error code 13 corresponds to EACCES). Verification Steps (What I have checked): Multicast Networking Entitlement is Approved and Applied: The necessary entitlement (com.apple.developer.networking.multicast) was granted by Apple. The Provisioning Profile used for signing the Host App Target has been regenerated and explicitly includes "Multicast Networking" capability (see attached screenshot). I confirmed that Entitlements cannot be added directly to the Framework Target, only the Host App Target, which is the expected behavior. Local Network Privacy is Configured: The Host App's Info.plist contains the NSLocalNetworkUsageDescription key with a clear usage string. Crucially, the Local Network Access alert does not reliably appear when the Broadcast function is first called (despite a full reinstall after OS upgrade). Even when Local Network Access is manually enabled in Settings, the Broadcast still fails with EACCES. Code Implementation: The Broadcast is attempted using NWConnection to the host 255.255.255.255 on a specific port. Request: Since all required entitlements and profiles are correct, and the failure is a low-level EACCES on a newly updated OS version, I suspect this may be a regression bug in the iPadOS 26 security sandbox when validating the Multicast Networking Entitlement against a low-level socket call (like sendmsg). Has anyone else encountered this specific Permission denied error on iPadOS 26 with a valid Multicast Entitlement, and is there a known workaround aside from switching to mDNS/Bonjour?

My application (using a nested framework for networking) was working correctly on iPadOS 18, but failed to perform a UDP broadcast operation after upgrading the device to iPadOS 28. The low-level console logs consistently show a "Permission denied" error. Symptoms & Error Message: When attempting to send a UDP broadcast packet using NWConnection (or a similar low-level socket call within the framework), the connection fails immediately with the following error logged in the console: nw_socket_service_writes_block_invoke [C2:1] sendmsg(fd 6, 124 bytes) [13: Permission denied] (Error code 13 corresponds to EACCES). Verification Steps (What I have checked): Multicast Networking Entitlement is Approved and Applied: The necessary entitlement (com.apple.developer.networking.multicast) was granted by Apple. The Provisioning Profile used for signing the Host App Target has been regenerated and explicitly includes "Multicast Networking" capability (see attached screenshot). I confirmed that Entitlements cannot be added directly to the Framework Target, only the Host App Target, which is the expected behavior. Local Network Privacy is Configured: The Host App's Info.plist contains the NSLocalNetworkUsageDescription key with a clear usage string. Crucially, the Local Network Access alert does not reliably appear when the Broadcast function is first called (despite a full reinstall after OS upgrade). Even when Local Network Access is manually enabled in Settings, the Broadcast still fails with EACCES. Code Implementation: The Broadcast is attempted using NWConnection to the host 255.255.255.255 on a specific port. Request: Since all required entitlements and profiles are correct, and the failure is a low-level EACCES on a newly updated OS version, I suspect this may be a regression bug in the iPadOS 28 security sandbox when validating the Multicast Networking Entitlement against a low-level socket call (like sendmsg). Has anyone else encountered this specific Permission denied error on iPadOS 28 with a valid Multicast Entitlement, and is there a known workaround aside from switching to mDNS/Bonjour?

Hello, We use the Network API in our macOS ObjectiveC applications to create a small web server. With macOS Sequoia or Tahoe (not with Sonoma), downloading files from another computer using the built-in ethernet port is way too slow. Steps to reproduce: Computer A (using macOS Tahoe or Sonoma), run an application using the Network APIs to create a webserver Make sure that this computer connects to the network using the Ethernet port, there is no issue when using WiFi On computer B, make an HTTP request to download a 20MB file => it will take about 30 seconds to download => way too slow... We tested with: if on computer A you run a web server using the GCD API instead of Network, it takes 0.2 seconds to download the file => no issue on computer A disable TSO, it improves the results, but that's not a long term solution as it doesn't hold when rebooting I can provide sample code to demonstrate this if needed. This is a new issue as it's been a while we use that code, and only noticed it recently, and macOS Sonoma is not impacted. Thank you for the help you can provide. Pierre

I am seeking assistance with how to properly handle / save / reuse NWConnections when it comes to the NWBrowser vs NWListener. Let me give some context surrounding why I am trying to do what I am. I am building an iOS app that has peer to peer functionality. The design is for a user (for our example the user is Bob) to have N number of devices that have my app installed on it. All these devices are near each other or on the same wifi network. As such I want all the devices to be able to discover each other and automatically connect to each other. For example if Bob had three devices (A, B, C) then A discovers B and C and has a connection to each, B discovers B and C and has a connection to each and finally C discovers A and B and has a connection to each. In the app there is a concept of a leader and a follower. A leader device issues commands to the follower devices. A follower device just waits for commands. For our example device A is the leader and devices B and C are followers. Any follower device can opt to become a leader. So if Bob taps the “become leader” button on device B - device B sends out a message to all the devices it’s connected to telling them it is becoming the new leader. Device B doesn’t need to do anything but device A needs to set itself as a follower. This detail is to show my need to have everyone connected to everyone. Please note that I am using .includePeerToPeer = true in my NWParameters. I am using http/3 and QUIC. I am using P12 identity for TLS1.3. I am successfully able to verify certs in sec_protocal_options_set_verify_block. I am able to establish connections - both from the NWBrowser and from NWListener. My issue is that it’s flaky. I found that I have to put a 3 second delay prior to establishing a connection to a peer found by the NWBrowser. I also opted to not save the incoming connection from NWListener. I only save the connection I created from the peer I found in NWBrowser. For this example there is Device X and Device Y. Device X discovers device Y and connects to it and saves the connection. Device Y discovers device X and connects to it and saves the connection. When things work they work great - I am able to send messages back and forth. Device X uses the saved connection to send a message to device Y and device Y uses the saved connection to send a message to device X. Now here come the questions. Do I save the connection I create from the peer I discovered from the NWBrowser? Do I save the connection I get from my NWListener via newConnectionHandler? And when I save a connection (be it from NWBrowser or NWListener) am I able to reuse it to send data over (ie “i am the new leader command”)? When my NWBrowser discovers a peer, should I be able to build a connection and connect to it immediately? I know if I save the connection I create from the peer I discover I am able to send messages with it. I know if I save the connection from NWListener - I am NOT able to send messages with it — but should I be able to? I have a deterministic algorithm for who makes a connection to who. Each device has an ID - it is a UUID I generate when the app loads - I store it in UserDefaults and the next time I try and fetch it so I’m not generating new UUIDs all the time. I set this deviceID as the name of the NWListener.Service I create. As a result the peer a NWBrowser discovers has the deviceID set as its name. Due to this the NWBrowser is able to determine if it should try and connect to the peer or if it should not because the discovered peer is going to try and connect to it. So the algorithm above would be great if I could save and use the connection from NWListener to send messages over.

Are the Wifi-Aware's WAEndpoint's discovered ephemeral? I'm trying to understand what's the best way to reconnect a disconnected WifiAware connection - Can I just cache the endpoint and start a new connection with the same endpoint or do I need to browse again and get a new WAEndpoint? My use case requires both WifiAware connection to another device and the devices also need to be connected to infrastructure wifi most of the time. I'm concerned about the WifiAware's connection having any impact on infrastructure wifi. What is the impact on the infrastructure wifi here in comparison to using the Apple peer to peer wifi(That Multipeer framework or Network framework use)?

Hi everyone 👋 I’m running into a persistent SSL issue on iOS where the app fails to establish a secure HTTPS connection to our backend APIs. The same endpoints work fine on Android and web, but on iOS the requests fail with: Error Domain=NSURLErrorDomain Code=-1200 "An SSL error has occurred and a secure connection to the server cannot be made." UserInfo={ NSLocalizedDescription = "An SSL error has occurred and a secure connection to the server cannot be made."; _kCFStreamErrorDomainKey = 3; _kCFStreamErrorCodeKey = -9802; } 🔍 What I’ve Checked: The servers use valid, trusted SSL certificates from a public CA TLS 1.2 and 1.3 are enabled The intermediate certificates appear correctly configured (verified using SSL Labs) The issue happens on our customer's end. (Got it via Sentry) Note: We recently removed NSAppTransportSecurity(NSAllowsArbitraryLoads) on our app, since all the endpoints use valid HTTPS certificates and standard configurations. ❓ Questions: Are there additional SSL validation checks performed by iOS when ATS is enabled? Has anyone seen similar behaviour, where valid certificate chains still trigger SSL errors? Any insights or debugging suggestions would be greatly appreciated 🙏

Explanation of the issue When tethering is enabled and a wireless connection is established, there are instances where an IP address is not assigned. Steps to Reproduce the Issue (if possible) Enable iPhone tethering and connect wirelessly using 11ax. Expected Result The iPhone assigns an IP address, enabling network connectivity. Actual Result Observed DHCP negotiation failed. After attempting communication with the DHCP server via DHCP Discover, a DHCP Offer was returned from the iPhone. If this was missed, it would retry by performing another DHCP Discover. However, the iPhone does not issue a DHCP Offer no matter how many times it retries. The IP address is not assigned unless the wireless connection is disconnected and reconnected. If the initial Discover is missed, does this invalidate subsequent Offer retries? The above issue has been confirmed on iPhone 17 Pro and iPhone 16. It does not appear to occur on iPhone 15.

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?

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.

Reproduce Same SIM card with 4G, same testing location, connected to the same server, xcode debugging game applications, network/profile retrotransmitted, Avg round trip to view data iPhone17， Turn off 4G and turn on WiFi. All the above indicators are acceptable iPhone17， Turn on 4G, turn off WiFi, retry with retransmission and very high Avg round trip iPhone14-16， Turn on 4G and turn off WiFi. All the above indicators are acceptable App Unity3d project .netframe4.0 C# Socket Other Many developers in Chinese forums have provided feedback on this issue

We have observed a per-process limitation on the number of simultaneous nw_connection_t objects in certain macOS environments. On some systems, this limit does not appear to apply, but on others the limitation is reproducible. When a process attempts to establish a large number of connections (e.g. 512+), some connections enter the nw_connection_state_waiting state and report the POSIX error “Cannot allocate memory”. These connections remain stuck indefinitely, even after other connections are deallocated and resources should theoretically be available again. This behavior severely impacts use cases such as transparent proxies implemented via the NetworkExtension framework, which intercept system-wide traffic and must open connections on behalf of all client processes. In this scenario, a per-process limit effectively becomes a system-wide limit, leading to unexpected and hard-to-diagnose network failures in client applications. So, is there any way to disable this restriction for Network Extension processes? Are there any system settings that could affect this limitation and be modified by users?

Hi Apple Engineers and fellow developers, I'm a student developer working on an educational focus management app that helps users hide distracting apps during study sessions. The app consists of: macOS app: Simple "Hide apps" button that triggers app hidding sessions iOS app: Uses Screen Time API to temporarily hide selected apps from home screen Communication: Bonjour networking between Mac and iPhone for session coordination The Challenge My app requires two entitlements that aren't available with Personal Developer Teams: com.apple.developer.family-controls (for Screen Time API) com.apple.developer.networking.multicast (for Bonjour device discovery) Current Error Messages text Cannot create a iOS App Development provisioning profile for "focuser.focuser-app". Personal development teams, including "My Name", do not support the Family Controls (Development) capability. Provisioning profile doesn't include the com.apple.developer.family-controls and com.apple.developer.networking.multicast entitlements. My Question for Apple Engineers Is there any legitimate way to test these privacy-sensitive APIs on my own devices for educational/learning purposes without purchasing the $99/year Apple Developer Program membership? I understand the security reasons behind these restrictions, but as a student just learning iOS development, it creates a significant barrier to experimenting with these technologies.

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.