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We are using NSURLSessionStreamTask for tcp communication. We would like to get the underlying bsd socket to disable the Nagel algorithm. The issue is we are always having a NULL socket handle (get kCFStreamPropertySocketNativeHandle property) from the NSInputStream/NSOutputStream captured from NSURLSessionStreamTask.Below are the steps how we get the raw socket handler:1. Create NSURLSessionStream by usingNSURLSessionStreamTask *_streamTask = [some_session streamTaskWithHostName:_hostname port:_port];2. Capture the steams of the task by using:[_streamTask captureStreams]3. Open streams in the delegate "updateInputStream: outputStream:"- (void)updateInputStream:(NSInputStream *)inputStream outputStream:(NSOutputStream *)outputStream { if (inputStream == nil || outputStream == nil) { return; } // Cache the stream so we can use later _inputStream = inputStream; _outputStream = outputStream; [_inputStream setDelegate:self]; [_outputStream setDelegate:self]; [_inputStream scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode]; [_outputStream scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode]; [_inputStream open]; [_outputStream open];}4. We can use the _inputStream and _outputStream to send/receive data to the remote host.5. However, when trying to get kCFStreamPropertySocketNativeHandle for this _inputStream/_outputStream, NULL is always returned.CFDataRef socketData = CFWriteStreamCopyProperty((__bridge CFWriteStreamRef)_outputStream), kCFStreamPropertySocketNativeHandle);I also tried with the _inputStream by using CFReadStreamCopyProperty, but still a NULL is returned.Any idea on why NULL is returned for the input/output streams captured from NSURLSesssionStreamTask?