Hi, in our project we use Network.framework, with NWListener and NWConnection, to send and receive data over UDP. We use the receiveMessage(completion:) API, which delivers the data as a Data object. We assign this Data to a property of one of our classes, which we continue to work with after the completion handler returns. We pass that property's bytes to our C++ code (through Swift–C++ interop) using Data.withUnsafeMutableBytes(_:). The C++ code modifies the bytes in place, and we then continue working with the modified Data in Swift. Since nothing else refers to the Data we received, the bytes are modified in place and no copy is made. However, if another Data value shared the same buffer, just calling withUnsafeMutableBytes(_:) would create a copy, whether or not we actually modified the bytes. Our understanding is that this is because the method is declared mutating, so the call itself is treated as a write and copy-on-write makes the buffer unique before the pointer is handed out. We also understand that ResultType : ~Copyable (along with the typed throws(E)) only relaxes the requirements on the closure's return type and doesn't affect this behaviour. We understand this approach is unsafe and that the pointer "should not be stored and used outside of the lifetime of the call to the closure", so we will take care of that. Since the typed-pointer variants of APIs such as Data.withUnsafeBytes were deprecated in Swift 5, we would also like to confirm that withUnsafeMutableBytes(_:), the variant that takes an UnsafeMutableRawBufferPointer, is the intended long-term API and isn't expected to be deprecated in the same way.

While going through the documentation for NWConnection, there seems to be state known as .waiting which means that the connection is waiting for a path change. For TCP, the state is understandable and can occur under some scenarios. But for the case of UDP, I have following queries: Why do we need .waiting state for the case of UDP? Even if we do need .waiting state for UDP, when all does this state occurs?

I’m using Network Framework with UDP and calling: connection.receive(minimumIncompleteLength: 1, maximumLength: 1500) { data, context, isComplete, error in ... // Some Logic } Is it possible for this completion handler to be called with data==nil if I haven't received any kind of error, i.e., error==nil and the connection is still in the .ready state?

Hello Everyone, I am currently using macOS 15.5 and XCode 16.4. I am using the following code to send/receive multicast packets on multicast group ff02::1 and port 49153 using Apple NF's NWConnectionGroup. import Network import Foundation // Creating a mutlicast group endpoint let multicastIPv6GroupEndpoint: NWEndpoint = NWEndpoint.hostPort(host: NWEndpoint.Host.ipv6(IPv6Address("ff02::1")!), port: NWEndpoint.Port("49153")!) do { let multicastGroupDescriptor: NWMulticastGroup = try NWMulticastGroup (for: [multicastIPv6GroupEndpoint]) let multicastConnectionGroupDescriptor = NWConnectionGroup (with: multicastGroupDescriptor, using: .udp) multicastConnectionGroupDescriptor.stateUpdateHandler = { state in print ("🕰️ Connection Group state: \(state)") if state == .ready { multicastConnectionGroupDescriptor.send (content: "👋🏻 Hello from the Mac 💻".data (using: .utf8)) { err in print ("➡️ Now, I am trying to send some messages.") if let err = err { print ("💥 Error sending multicast message: \(err)") } else { print ("🌚 Initial multicast message sent") } } } } multicastConnectionGroupDescriptor.setReceiveHandler { message, content, isComplete in if let content = content, let messageString = String (data: content, encoding: .utf8) { print ("⬅️ Received message: \(messageString)") } } multicastConnectionGroupDescriptor.start (queue: .global()) } catch { print ("💥 Error while creating Multicast Group: \(error)") } RunLoop.main.run() I am able to successfully create a NWConnectionGroup without any warnings/errors. The issue occurs when the stateUpdateHandler's callback gets invoked. It first gives me this warning: nw_listener_socket_inbox_create_socket IPV6_LEAVE_GROUP ff02::1.49153 failed [49: Can't assign requested address But then it shows me that the state is ready: 🕰️ Connection Group state: ready After this, when the send is performed, it gives me a bunch of errros: nw_endpoint_flow_failed_with_error [C1 ff02::1.49153 waiting parent-flow (unsatisfied (Local network prohibited), interface: en0[802.11], ipv4, ipv6, uses wifi)] already failing, returning nw_socket_connect [C1:1] connectx(7, [srcif=0, srcaddr=::.62838, dstaddr=ff02::1.49153], SAE_ASSOCID_ANY, 0, NULL, 0, NULL, SAE_CONNID_ANY) failed: [48: Address already in use] nw_socket_connect [C1:1] connectx failed (fd 7) [48: Address already in use] nw_socket_connect connectx failed [48: Address already in use] nw_endpoint_flow_failed_with_error [C1 ff02::1.49153 in_progress socket-flow (satisfied (Path is satisfied), interface: en0[802.11], ipv4, ipv6, dns, uses wifi)] already failing, returning There is no other background process running on the same port. I tried using different ports as well as multicast groups but the same error persists. The same code works fine for an IPv4 multicast group. I have following questions: Why am I getting these errors specifically for IPv6 multicast group but not for IPv4 multicast group? Are there any configurations that needed to be done in order to get this working?