title: How to download from FTP via NSURLSessionStreamTask?
body: <p>Before iOS 9, I use the CFStream APIs (which are deprecated after iOS 9) to list / download / upload files via FTP.</p>
  
  <p>Now, I have to transfer my program to adapt iOS 9. </p>
  
  <p>How can I download files from FTP via NSURLSessionStreamTask?</p>