title: How to get the upload progress when using sockets?
body: <p>When downloading a file, I know how much data has been downloaded and so I can show the download progress.</p>
  
  <p>However, when uploading a file, I don't really know how much data has been received by the other end and so I can't show the upload progress, so I'm thinking that the only way to know how much data has been uploaded is by making the receiver send back to me how much data has been received every time some data is received.</p>
  
  <p>Is this correct or is there's another way?</p>