Thanks @DTS Engineer . I now understand that the dispatch queue holds a strong reference to the closures, and those closures are only released once they run. If the queue is suspended and the closures never execute, those references are never released and the memory remains retained indefinitely. In my case, I suspended the dispatch queue only to simulate certain scenarios - I don’t intend to suspend the queue. My main question was whether, after calling .cancel() on an NWConnection, I need to wait for confirmation from the OS that the pending I/O has actually been cancelled. Based on our discussion on the thread, my understanding is that I do not need to wait. Is that correct? To restate the scenario: If I call .cancel() on the NWConnection and then release my own reference to the dispatch queue (e.g., set it to nil), the NWConnection still holds a strong reference to that queue. So the queue won’t be released until the NWConnection itself completes its teardown. My understanding is that .cancel() begins tearing down the NWConnection, and even if cancellation of the pending I/O is delayed, the NWConnection will eventually drop its reference to the queue as part of its cleanup, without waiting for any pending send/receive closures to execute. Since the closures themselves do not hold a strong reference back to the NWConnection, the teardown does not wait for those closures to run before releasing its reference to the queue. Right?

Thanks @DTS Engineer, However, that’s not a problem because, in general, you shouldn’t rely on releasing the last reference to cancel the connection. Rather, you should call cancel() on it. That’s guaranteed to complete all the outstanding receives which breaks any retain loops they might’ve formed. Some Questions: When we call .cancel, the teardown begins and all pending receives are supposed to be cancelled. If I suspend the dispatch queue on which async events for the NWConnection are delivered, the cancellation callbacks will not be invoked. In that case, will the reference held by the receive closure remain unreleased, potentially causing a memory leak if the receive closure holds a strong reference to another object? 2 And if the receive closure does not hold a strong reference, then even if the callback is not invoked, it should not be a problem, right?

Thanks @DTS Engineer , No. From the perspective of Network framework, the cancellation will proceed asynchronously and that’s just fine. However, it’s easy to think of cases where you might need to do that due to considerations in your code. Imagine, for example, that you have a listener controlled by a Start / Stop button. If the user clicks Stop and then immediately clicks Start, bad things might happen if the cancellation is still in progress. In that case, you’d want to show a status of stopping and not enable the Start button until the cancellation is complete. I understand that the application does not need to wait for OS confirmation, and it can simply exit and that this is safe to do. However, in the case where I am restarting my application, it seems possible that if I restart without waiting for the listener’s cancellation confirmation, I might not be able to open the listener on the same port because it is still busy, resulting in a 'port/address in use' error. Is this understanding correct, and are there any implications other than this?

Thanks, @DTS Engineer (Kevin). I think there's been a misunderstanding regarding my doubt about the OperationQueue concurrency limit. Since I’m using an OperationQueue with a defined concurrency limit, the number of tasks executing concurrently depends on this limit. As I am the one scheduling tasks through the OperationQueue, the concurrency level will be controlled by the set limit. Now, in the case of Apple's Network Framework, we need to provide a dispatch queue (The queue on which listener events are delivered). If I pass the same dispatch queue that the OperationQueue uses internally, will this affect the number of callbacks executed concurrently? Or does the OperationQueue concurrency limit have no impact on callback execution?

Hi @DTS Engineer (Kevin), Concurrent queues are a relatively late addition to the API and, IMHO, are something that you should actively avoid, as they create exactly the same issues as the global concurrent queues.The ONE exception to that is cases where you're specifically trying to create a limited amount of parallel activity with a specific component ("up to 4 jobs at once"). IF that's the case, then the correct solution would be to use NSOperationQueue to set the width. As a side note here, NSOperationQueue is actually the API I would recommend over dispatch for case where you want something that works like GCD. It's built as a wrapper around dispatch, however, it also provides things like a common work object base class, cancellation, progress, etc. It also exports the underlying GCD queue, so you can also use it with any API that requires a GCD queue. As per your suggestion i tried using OperationQueue, which provide[s] us the capability of controlling the number of Concurrent Task[s] by specifying the maxConcurrentTask[s] property of the Operation Queue. To test this, I created an OperationQueue with QOS set to default and concurrent attributes to allow multiple tasks to run in parallel. I then set maxConcurrentOperationCount = 2 and passed the queue to the .start call of NWListener. Next, I sent 10 concurrent connections from another machine to observe whether only 2 connections would be processed at a time. However, despite setting maxConcurrentOperationCount, all 10 connections were handled simultaneously. It appears that the underlying dispatch queue is bypassing the concurrency limit. import Network import Foundation var operation_queue = OperationQueue () operation_queue.underlyingQueue = DispatchQueue (label: "test_operation_queue", qos: .default, attributes: .concurrent) operation_queue.maxConcurrentOperationCount = 2 do { var params = NWParameters(tls: NWProtocolTLS.Options (), tcp: NWProtocolTCP.Options()) let listener = try NWListener(using: params, on: 52000) // Use a specific port listener.stateUpdateHandler = { state in switch state { case .setup: print("Setup state") case .waiting(let error): print("Waiting state with error: \(error)") case .ready: print("Server is ready on port \(listener.port ?? 0)") case .failed(let error): print("Failed state with error: \(error)") case .cancelled: print("Cancelled state") @unknown default: print("Unknown state") } } listener.newConnectionHandler = {connection in print ("Connection Received and processing Started") } listener.start(queue: operation_queue.underlyingQueue!) } catch { print("Failed to create listener: \(error)") } Am I missing something here?

@DTS Engineer I know this that swift::Bool is compatible with c++ bool. What I wanted to ask is that in the documentation it is mentioned that Swift exposes UnsafeMutablePointer to C++ (link). Quote Pointer types, like OpaquePointer, UnsafePointer, UnsafeMutablePointer, UnsafeRawPointer and UnsafeMutableRawPointer UnQuote I directly want to use them in c++ as swift::UnsafeMutablePointer. If it's not true what documentation mean, then what is the manifestation for exposing these UnsafeMutablePointer?

@DTS Engineer I got your point and i was able to use the pointer in that way. public func ReturnInteger() -> UnsafeMutablePointer<Int32> { withUnsafeMutablePointer(to: &value) {pointer in return pointer } } void CppClass::GetIntegerPointer() noexcept { int32_t * x = (int32_t *)Interop::ReturnInteger(); // The above way works but when i am trying to directly use // swift::UnsafeMutablePointer<int32_t> x = (int32_t *) Interop::ReturnInteger (); // it gives build error that UnsafeMutablePointer not found . } But in the documentation it's mentioned that it is exposed to C++. Quote Pointer types, like OpaquePointer, UnsafePointer, UnsafeMutablePointer, UnsafeRawPointer and UnsafeMutableRawPointer UnQuote Can you Explain what does this mean?

@Claude31 I can't use class type as this Data instance is provided to me by the OS whenever my Completion is been called w.r.t Receive. Now I want to use this data instance in C++. For which basically I create a wrapper class over this and pass it as Opaque to C++. Code Snippet class DataHolder { init () {} public var data_wrapper : Data? } func ReceiveHandler (_ pContent : Data? ) -> UnsafeMutablePointer { // pContent is only valid inside scope of this function . // Create a instance of wrapper class var x = DataHolder.init () // Copy being created here. x.data_wrapper = pContent return Unmanaged.passRetained (x).toOpaque () } Problem is copy creation each time which i want to prevent.

@DTS Engineer Thanks I got the clarity regarding the ARC. I have a usecase where I get a Data Object in the CallBack I Register during the receive call. I want to pass the same Data Object to C++ without creating a Copy and ensuring that it remains valid until i am done with my operations in C++. Is there a way for that?

Hi @DTS Engineer, withUnsafeBytes is Deprecated with data Now, is there any other alternative way to do this. Also just wanted to confirm that within the closure the Pointer to the bytes will always remain valid and it's ARC will not be decremented any how?

Yes It's related to Active Directory. Here I am not referring to the FQDN of the interfaces through which we are connected to Internet. Just like hostname which helps us to identify a machine in a network. We can use network-name (local domain name) which is assigned to a machine and doesn't depend on the interfaces, which can be used as an alternative of an IP-address. Fully Qualified Domain Name which i means is hostname + network name (local domain name) which can be used to communicate with a machine.

No, i require the local domain assigned to a machine, just like we have in Windows. Hostname is used to identify a machine in network. I am able to get the hostname, how can i get FQDN (Fully Qualified Domain Name) which will be consisting of hostname.networkname for Ex - macofficestudio is my host name and thread.solutions.com is my network name (local domain name) so FQDN becomes macofficestudio.thread.solutions.com. How to get that ??