Hello, I'm experiencing an issue with my app where it's being terminated by the system with a watchdog violation during back-to-back messaging operations. I've analyzed the crash logs but would appreciate additional insights on optimizing my approach. I'd appreciate any insights on how to resolve this problem. Crash Details: Exception Type: EXC_CRASH (SIGKILL) Termination Reason: FRONTBOARD with code 0x8BADF00D Error: "scene-update watchdog transgression: app exhausted real time allowance of 10.00 seconds" Reproduction Steps: User A initiates back-to-back messages to other User User A's UI becomes unresponsive and eventually the app crashes. Stack Trace Analysis: The crash occurs on the main thread, which appears to be blocked waiting for a condition in the keyboard handling system. The thread is stuck in [UIKeyboardTaskQueue _lockWhenReadyForMainThread] and related methods, suggesting an issue with keyboard-related operations during the messaging process. Crash Tag Exception Type: EXC_CRASH (SIGKILL) Exception Codes: 0x0000000000000000, 0x0000000000000000 Termination Reason: FRONTBOARD 2343432205 <RBSTerminateContext| domain:10 code:0x8BADF00D explanation:scene-update watchdog transgression: app<com.msikodiak.eptt(AD934F8A-DF57-4B75-BE73-8CF1A9A8F856)>:301 exhausted real (wall clock) time allowance of 10.00 seconds ProcessVisibility: Foreground ProcessState: Running WatchdogEvent: scene-update WatchdogVisibility: Background WatchdogCPUStatistics: ( "Elapsed total CPU time (seconds): 6.390 (user 3.640, system 2.750), 11% CPU", "Elapsed application CPU time (seconds): 0.020, 0% CPU" ) ThermalInfo: ( "Thermal Level: 0", "Thermal State: nominal" ) reportType:CrashLog maxTerminationResistance:Interactive> Triggered by Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 libsystem_kernel.dylib 0x1e773d438 __psynch_cvwait + 8 1 libsystem_pthread.dylib 0x2210bc328 _pthread_cond_wait + 1028 2 Foundation 0x1957d8a64 -[NSCondition waitUntilDate:] + 132 3 Foundation 0x1957d8888 -[NSConditionLock lockWhenCondition:beforeDate:] + 80 4 UIKitCore 0x1998f1238 -[UIKeyboardTaskQueue _lockWhenReadyForMainThread] + 456 5 UIKitCore 0x19a3d775c __59-[UIKeyboardImpl updateAutocorrectPrompt:executionContext:]_block_invoke_9 + 28 6 UIKitCore 0x19986b084 -[UIKeyboardTaskQueue lockWhenReadyForMainThread] + 168 7 UIKitCore 0x19a3f2994 -[UIKeyboardTaskQueue waitUntilTaskIsFinished:] + 148 8 UIKitCore 0x19a3f2ac4 -[UIKeyboardTaskQueue performSingleTask:breadcrumb:] + 132 9 UIKitCore 0x199e2f7e4 -[_UIKeyboardStateManager updateForChangedSelection] + 144 10 UIKitCore 0x199e24200 -[_UIKeyboardStateManager invalidateTextEntryContextForTextInput:] + 92 11 WebKit 0x1ad52fa54 WebKit::PageClientImpl::didProgrammaticallyClearFocusedElement(WebCore::ElementContext&&) + 40 12 WebKit 0x1ad55adcc WebKit::WebPageProxy::didProgrammaticallyClearFocusedElement(WebCore::ElementContext&&) + 136 13 WebKit 0x1acec74e8 WebKit::WebPageProxy::didReceiveMessage(IPC::Connection&, IPC::Decoder&) + 18604 14 WebKit 0x1acd21184 IPC::MessageReceiverMap::dispatchMessage(IPC::Connection&, IPC::Decoder&) + 236 15 WebKit 0x1ace449b8 WebKit::WebProcessProxy::dispatchMessage(IPC::Connection&, IPC::Decoder&) + 40 16 WebKit 0x1ace44228 WebKit::WebProcessProxy::didReceiveMessage(IPC::Connection&, IPC::Decoder&) + 1764 17 WebKit 0x1acd1e904 IPC::Connection::dispatchMessage(WTF::UniqueRef<IPC::Decoder>) + 268 18 WebKit 0x1acd1e478 IPC::Connection::dispatchIncomingMessages() + 576 19 JavaScriptCore 0x1ae386b8c WTF::RunLoop::performWork() + 524 20 JavaScriptCore 0x1ae386960 WTF::RunLoop::performWork(void*) + 36 21 CoreFoundation 0x196badce4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28 22 CoreFoundation 0x196badc78 __CFRunLoopDoSource0 + 172 23 CoreFoundation 0x196bac9fc __CFRunLoopDoSources0 + 232 24 CoreFoundation 0x196babc3c __CFRunLoopRun + 840 25 CoreFoundation 0x196bd0700 CFRunLoopRunSpecific + 572 26 GraphicsServices 0x1e3711190 GSEventRunModal + 168 27 UIKitCore 0x1997ee240 -[UIApplication _run] + 816 28 UIKitCore 0x1997ec470 UIApplicationMain + 336 29 Telstra PTT 0x1004d30c8 main + 56 30 dyld 0x1bd5d3ad8 start + 5964

Will App be terminated or suspended when updating to incremental version from app store?

I am building a Mac app that launch a GUI helper app and use XPC to communicate between them. Main app start a XPC Listener using NSXPCListener(machServiceName: "group.com.mycompany.myapp.xpc") Launch the helper app Helper app connect to the XPC service and listen command from main app. What I observe is the app seems can start XPC listener while I run it via Xcode. If I run the app using TestFlight build, or via the compiled debug binary (same one that I use on Xcode), it cannot start the XPC service. Here is what I see in the Console: [0x600000ef7570] activating connection: mach=true listener=true peer=false name=group.com.mycompany.myapp.xpc [0x600000ef7570] listener failed to activate: xpc_error=[1: Operation not permitted] Both main app and helper app are sandboxed and in the same App Group - if they were not, I cannot connect the helper app to main app. I can confirm the entitlement profiles did contain the app group. If I start the main app via xcode, and then launch the helper app manually via Finder, the helper app can connect to the XPC and everything work. It is not related to Release configuration, as the same binary work while I am debugging, but not when I open the binary manually. For context, the main app is a Catalyst app, and helper app is an AppKit app. To start a XPC listener on Catalyst, I had do it in a AppKit bridge via bundle. Given the app worked on Xcode, I believe this approach can work. I just cannot figure out why it only work while I am debugging. Any pointer to debug this issue is greatly appreciated. Thanks!

For this code: let status = try await container.accountStatus() Seeing this error: 2025-05-08 15:32:00.945731-0500 localhost myAgent[2661]: (myDaemon.debug.dylib) [com.myDaemon.cli:networking] Error Domain=CKErrorDomain Code=6 "Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error." UserInfo={NSLocalizedDescription=Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error., CKRetryAfter=5, CKErrorDescription=Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error., NSUnderlyingError=0x600001bfc270 {Error Domain=NSCocoaErrorDomain Code=4099 UserInfo={NSDebugDescription= I initially started the this process as System Daemon to see what would happen (which obviously does not have CloudKit features). Then moved it back to /Library/LaunchAgents/ and can't get rid of that error. I see also following message from CloudKit daemon: Ignoring failed attempt to get container proxy for &lt;private&gt;: Error Domain=NSCocoaErrorDomain Code=4099 UserInfo={NSDebugDescription=&lt;private&gt;} Automatically retrying getting container proxy due to error for &lt;private&gt;: Error Domain=NSCocoaErrorDomain Code=4099 UserInfo={NSDebugDescription=&lt;private&gt;} XPC connection interrupted for &lt;private&gt; And this error for xpc service: [0x130e074b0] failed to do a bootstrap look-up: xpc_error=[3: No such process] If I start the same cli process directly from XCode, then it works just fine.

I am building an app that uses the SMAppService to register a LaunchDaemon that is bundled with my .app. I've got a priming flow created which walks the user through approving the service so that it will start on login. However, I need to also be able to upgrade this background service if the user updates the app. To do this, I think I need to call unregisterAndReturnError and then registerAndReturnError. From my testing, this seems to work correctly, but I have a concern. Will the user ever be prompted to re-authorize the LaunchDaemon that I am registering? If so, under what circumstances will that happen, and what does it look like (so that I can guide the user through it)?

I have been playing with application bundled LaunchAgents: I downloaded Apple sample code, Run the sample code as is, Tweaked the sample code a lot and changed the LaunchAgents IDs and Mach ports IDs, Created new projects with the learnings, etc. After deleting all the Xcode projects and related project products and rebooting my machine several times, I noticed the LaunchAgent are still hanging around in launchctl. If I write launchctl print-disabled gui/$UID (or user/$UID) I can see all my testing service-ids: disabled services = { "com.xpc.example.agent" => disabled "io.dehesa.apple.app.agent" => disabled "io.dehesa.sample.app.agent" => disabled "io.dehesa.example.agent" => disabled "io.dehesa.swift.xpc.updater" => disabled "io.dehesa.swift.agent" => disabled } (there are more service-ids in that list, but I removed them for brevity purposes). I can enable or disable them with launchctl enable/disable service-target, but I cannot really do anything else because their app bundle and therefore PLIST definition are not there anymore. How can I completely remove them from my system? More worryingly, I noticed that if I try to create new projects with bundled LaunchAgents and try to reuse one of those service-ids, then the LaunchAgent will refuse to run (when it was running ok previously). The calls to SMAppService APIs such .agent(plistName:) and register() would work, though.

I’m working with apple dispatch queue in C with the following design: multiple dispatch queues enqueue tasks into a shared context, and a dedicated dispatch queue (let’s call it dispatch queue A) processes these tasks. However, it seems this design has a memory visibility issue. Here’s a simplified version of my setup: I have a shared_context struct that holds: task_lis: a list that stores tasks to be prioritized and run — this list is only modified/processed by dispatch queue A (a serially dispatch queue), so I don't lock around it. cross_thread_tasks: a list that other queues push tasks into, protected by a lock. Other dispatch queues call a function schedule_task that locks and appends a new task to cross_thread_tasks call dispatch_after_f() to schedule a process_task() on dispatch queue A process_task() that processes the task_list and is repeatedly scheduled on dispatch queue A : Swaps cross_thread_tasks into a local list (with locking). Pushes the tasks into task_list. Runs tasks from task_list. Reschedules itself via dispatch_after_f(). Problem: Sometimes the tasks pushed from other threads don’t seem to show up in task_list when process_task() runs. The task_list appears to be missing them, as if the cross-thread tasks aren’t visible. However, if the process_task() is dispatched from the same thread the tasks originate, everything works fine. It seems to be a memory visibility or synchronization issue. Since I only lock around cross_thread_tasks, could it be that changes to task_list (even though modified on dispatch queue A only) are not being properly synchronized or visible across threads? My questions What’s the best practice to ensure shared context is consistently visible across threads when using dispatch queues? Is it mandatory to lock around all tasks? I would love to minimize/avoid lock if possible. Any guidance, debugging tips, or architectural suggestions would be appreciated! =============================== And here is pseudocode of my setup if it helps: struct shared_data { struct linked_list* task_list; } struct shared_context { struct shared_data *data; struct linked_list* cross_thread_tasks; struct thread_mutex* lock; // lock is used to protect cross_thread_tasks } static void s_process_task(void* shared_context){ struct linked_list* local_tasks; // lock and swap the cross_thread_tasks into a local linked list lock(shared_context->lock) swap(shared_context->cross_thread_tasks, local_tasks) unlock(shared_context->lock) // I didnt use lock to protect `shared_context->data` as they are only touched within dispatch queue A in this function. for (task : local_tasks) { linked_list_push(shared_context->data->task_list) } // If the `process_task()` block is dispatched from `schedule_task()` where the task is created, the `shared_context` will be able to access the task properly otherwise not. for (task : shared_context->data->task_list) { run_task_if_timestamp_is_now(task) } timestamp = get_next_timestamp(shared_context->data->task_list) dispatch_after_f(timestamp, dispatch_queueA, shared_context, process_task); } // On dispatch queue B static void schedule_task(struct task* task, void* shared_context) { lock(shared_context->lock) push(shared_context->cross_thread_tasks, task) unlock(shared_context->lock) timestamp = get_timestamp(task) // we only dispatch the task if the timestamp < 1 second. We did this to avoid the dispatch queue schedule the task too far ahead and prevent the shutdown process. Therefore, not all task will be dispatched from the thread it created. if(timestamp < 1 second) dispatch_after_f(timestamp, dispatch_queueA, shared_context, process_task); }

Dear Apple Support Team, My app, io.cylonix.sase, has a BGAppRefreshTask (io.cylonix.sase.ios.refresh) that is canceled by dasd ~9ms after submission from a Network Extension. Please help identify the cause and suggest a solution. App Details: App ID: io.cylonix.sase iOS Version: 17.1.1 (iPhone Xs Max) Network Extension: saseWgNetworkExtension with packet-tunnel-provider entitlement Use Case: VPN app; Network Extension records file receipts in shared group UserDefaults and schedules BGAppRefreshTask to wake the main app. App Usage: High (frequently used) System State: Sufficient resources (not low on battery or memory) Issue: The task is submitted but canceled immediately with priority 10. It has never run, so rate-limiting is not an issue. ` debug 22:09:37.952749-0700 dasd Best binding found for evaluator 0x16d541720: &lt;private&gt; debug 22:09:37.954483-0700 dasd Invoking selector backgroundTaskSchedulerPermittedIdentifiersWithContext:tableID:unitID:unitBytes: on &lt;LSApplicationRecord 0x724844650&gt; default 22:09:37.955563-0700 dasd CANCELED: bgRefresh-io.cylonix.sase.ios.refresh:ABDAFA at priority 10 &lt;private&gt;!

When I search, it's always people trying to do stuff in the background. I want my app to only do stuff when it is active. And this post https://developer.apple.com/forums/thread/685525 seems to have prevented replies from the start. Which means it's just a documentation page and does not belong in the discussion forums at all, because it prevents all discussion.

How can you force cancel a task that doesn't need cleanup and doesn't check for cancellation? If this cannot be done, would this be a useful addition to Swift? Here is the situation: The async method doesn't check for cancellation since it is not doing anything repetively (for example in a loop). For example, the method may be doing "try JSONDecoder().decode(Dictionary<String, ...>.self, from: data)" where data is a large amount. The method doesn't need cleanup. I would like the force cancellation to throw an error. I am already handling errors for the async method. My intended situation if that the user request the async method to get some JSON encoded data, but since it is taking longer that they are willing to wait, they would tap a cancellation button that the app provides.

Hi, I have some questions regarding the Background Assets Extension and DeviceCheck framework. Goal: Ensure that only users who have purchased the app can access the server's API without any user authentication using for example DeviceCheck framework and within a Background Assets Extension. My app relies on external assets, which I'm loading using the Background Assets Extension. I'm trying to determine if it's possible to obtain a challenge from the server and send a DeviceCheck assertion during this process within the Background Assets Extension. So far, I only receive session-wide authentication challenges—specifically NSURLAuthenticationMethodServerTrust in the Background Assets Extensio. I’ve tested with Basic Auth (NSURLAuthenticationMethodHTTPBasic) just for experimentation, but the delegate func backgroundDownload( _ download: BADownload, didReceive challenge: URLAuthenticationChallenge ) async -> (URLSession.AuthChallengeDisposition, URLCredential?) is never called with that authentication method. It seems task-specific challenges aren't coming through at all. Also, while the DCAppAttestService API appears to be available on macOS, DCAppAttestService.isSupported always returns false (in my testing), which suggests it's not actually supported on macOS. Can anyone confirm if that’s expected behavior?

I have an app that uses background audio recording. From what others say, I have enabled the audio background mode to keep the audio session active, and this worked. But when submitting the app to the app store, the app was rejected because the audio background mode is only supposed to be used for audio playback. How do I create this background mode while following Apple's guidelines?

We've seen a recent increase in background terminations: blue - System Pressure orange - Task Timeout I'm trying to understand the increase in system-pressure terminations, since there's no corresponding increase in memory at suspension. Are there other system resources for which iOS will terminate an app?

My load average on a largely idle system is around 22, going up to 70 or so periodically; SSMenuAgent seems to be consuming lots of CPU (and, looking at spindump, it certainly seems busy), but... it's not happening on any other system whose screens I am observing. (Er, I know about load average limitations, the process is also consuming 70-98% CPU according to both top and Activity Monitor.) Since this machine (although idle) has our network extension, I'm trying to figure out if this is due to that, or of this is generally expected. Anyone?

We would be creating N NWListener objects and M NWConnection objects in our process' communication subsystem to create server sockets, accepted client sockets on server and client sockets on clients. Both NWConnection and NWListener rely on DispatchQueue to deliver state changes, incoming connections, send/recv completions etc. What DispatchQueues should I use and why? Global Concurrent Dispatch Queue (and which QoS?) for all NWConnection and NWListener One custom concurrent queue (which QoS?) for all NWConnection and NWListener? (Does that anyways get targetted to one of the global queues?) One custom concurrent queue per NWConnection and NWListener though all targetted to Global Concurrent Dispatch Queue (and which QoS?)? One custom concurrent queue per NWConnection and NWListener though all targetted to single target custom concurrent queue? For every option above, how am I impacted in terms of parallelism, concurrency, throughput &amp; latency and how is overall system impacted (with other processes also running)? Seperate questions (sorry for the digression): Are global concurrent queues specific to a process or shared across all processes on a device? Can I safely use setSpecific on global dispatch queues in our app?

I understand that GCD and it's underlying implementations have evolved over time. And many things have not been shared explicitly in Apple documentation. The most concepts of DispatchQueue (serial and concurrent queues), DispatchQoS, target queue and system provided queues: main and globals etc. I have some doubts & questions to clarify: [Main Dispatch Queue] [Link] Because the main queue doesn't behave entirely like a regular serial queue, it may have unwanted side-effects when used in processes that are not UI apps (daemons). For such processes, the main queue should be avoided. What does it mean? Can you elaborate? [Global Concurrent Dispatch Queues] Are they global to a process or across processes on a device. I believe it is the first case but just wanted to be sure. [Global Concurrent Dispatch Queues] Does system create 4 (for each QoS) * 2 (over-commiting and non-overcommiting queues) = 8 queues in all. When does which type of queue comes into play? [Custom Queue][Target Queue concept] [swift-corelibs-libdispatch/man/dispatch_queue_create.3] QUOTE The default target queue of all dispatch objects created by the application is the default priority global concurrent queue. UNQUOTE Is this stil true? We could not find a mention of this in any latest official apple documentation (though some old forum threads (one more) and github code documentation indicate the same). The official documentation only says: [dispatch_set_target_queue] QUOTE If you want the system to provide a queue that is appropriate for the current object UNQUOTE [dispatch_queue_create_with_target] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT to set the target queue to the default type for the current dispatch queue.UNQUOTE [Dispatch>DispatchQueue>init] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT if you want the system to provide a queue that is appropriate for the current object. UNQUOTE What is the difference between passing target queue as 'nil' vs 'DISPATCH_TARGET_QUEUE_DEFAULT' to DispatchQueue init? [Custom Queue][Target Queue concept] [dispatch_set_target_queue] QUOTE The system doesn't allocate threads to the dispatch queue if it has a target queue, unless that target queue is a global concurrent queue. UNQUOTE The system does allocate threads to the custom dispatch queues that have global concurrent queue as the default target. What does that mean? Why does targetting to global concurrent queues mean in that case? [System / GCD Thread Pool] that excutes work items from DispatchQueue: Is this thread pool per queue? or across queues per process? or across processes per device?

I'm looking into a newer XPC API available starting with macOS 14. Although it's declared as a low-level API I can't figure it how to specify code signing requirement using XPCListener and XPCSession. How do I connect it with xpc_listener_set_peer_code_signing_requirement and xpc_connection_set_peer_code_signing_requirement which require xpc_listener_t and xpc_connection_t respectively? Foundation XPC is declared as a high-level API and provides easy ways to specify code signing requirements on both ends of xpc. I'm confused with all these XPC APIs and their future: Newer really high-level XPCListener and XPCSession API (in low-level framework???) Low-level xpc_listener_t & xpc_connection_t -like API. Is it being replaced by newer XPCListener and XPCSession? How is it related to High-level Foundation XPC? Are NSXPCListener and NSXPCConnection going to be deprecated and replaced by XPCListener and XPCSession??

I'm working on an enterprise product that's mainly a daemon (with Endpoint Security) without any GUI component. I'm looking into the update process for daemons/agents that was introduced with Ventura (Link), but I have to say that the entire process is just deeply unfun. Really can't stress this enough how unfun. Anyway... The product bundle now contains a dedicated Swift executable that calls SMAppService.register for both the daemon and agent. It registers the app in the system preferences login items menu, but I also get an error. Error registering daemon: Error Domain=SMAppServiceErrorDomain Code=1 "Operation not permitted" UserInfo={NSLocalizedFailureReason=Operation not permitted} What could be the reason? I wouldn't need to activate the items, I just need them to be added to the list, so that I can control them via launchctl. Which leads me to my next question, how can I control bundled daemons/agents via launchctl? I tried to use launchctl enable and bootstrap, just like I do with daemons under /Library/LaunchDaemons, but all I get is sudo launchctl enable system/com.identifier.daemon sudo launchctl bootstrap /Path/to/daemon/launchdplist/inside/bundle/Library/LaunchDaemons/com.blub.plist Bootstrap failed: 5: Input/output error (not super helpful error message) I'm really frustrated by the complexity of this process and all of its pitfalls.

Hello, I am currently developing an iOS application using SensorKit. I encountered an issue when attempting to fetch SensorKit data in the background using background tasks (appRefresh, processing). The following error occurs: In the delegate function func sensorReader(_ reader: SRSensorReader, fetching fetchRequest: SRFetchRequest, failedWithError error: any Error) {}, I receive the error: SRErrorDataInaccessible. In code specific manner: start and handle background fetch (appRefresh) func handleAppRefreshTask(task: BGAppRefreshTask) { logger.logWithServer(level: .default, message: "background fetch start", category: String(describing: BackgroundTaskManager.self)) scheduleBackgroundFetch() let queue = OperationQueue() queue.maxConcurrentOperationCount = 1 let fetchOperation = FetchOperation() queue.addOperation(fetchOperation) task.expirationHandler = { self.logger.logWithServer(level: .error, message: "background fetch expirated", category: String(describing: BackgroundTaskManager.self)) queue.cancelAllOperations() } fetchOperation.completionBlock = { task.setTaskCompleted(success: !fetchOperation.isCancelled) } } Background fetch operation class class FetchOperation: Operation { override func main() { guard !isCancelled else { return } Task { // this function will execute fetch request for all user allowed sensorReader, 'func fetch(_ request: SRFetchRequest)' await SensorkitManager.shared.startFetchAndUpload() } } } I have the following questions: Is it possible to fetch SensorKit data in the background? If it is possible, why does the above error occur? If it is possible, could you provide the solution code and the correct workflow to avoid this error? Thank you.

Let's image that someone wants to use a background service to keep track of FSEvents activity, at the file level (a firehose, some might say). I choose this example, to indicate the volume and rate of data transmission in question. I'm not creating a front-end for FSEvents data, but my background service may generate data at a similar pace. The service runs off of user defined document/s that specify the FSEvent background filtering to be applied. Those that match get stored into a database. But filters can match on almost all the data being emitted by FSEvents. The user decides to check on the service's activity and database writes by launching a GUI that sends requests to the background service using XPC. So the GUI can request historic data from a database, but also get a real-time view of what FS events the service is busy filtering. So it's a client-server approach, that's concerned with monitoring an event stream over XPC. I understand XPC is a request/response mechanism, and I might look into using a reverse connection here, but my main concern is one of performance. Is XPC capable of coping with such a high volume of data transmision? Could it cope with 1000s of rows of table data updates per second sent to a GUI frontend? I know there are streaming protocol options that involve a TCP connection, but I really want to stay away from opening sockets.