There isn't a real good way to do this, when the client is using a browser. See Mega upload for a method that mixes Php and Perl. It's kind of complicated, where the server cgi script, passes the output to another report cgi. The upload cgi watches the upload progress in bytes, and the report cgi reports it back to the client. It involves javascript, and takes bandwidth (which slows your upload).

I played with it, and concluded it was just easier to make a javascript animation that starts when the upload starts, and finishes when it's done. See javascript upload indicator (The test script dosn't work online, because my el-cheapo hosting service dosn't allow Perl, but only Php. ) :-( I hav'nt tested these scripts in a long time, so take them as they are, they worked way back when.

Now if I want a progressbar on uploads, I write a Tk script to do it. Can you give your clients a Tk or Gtk2 script?