Code:
  sockwrite -n $sockname POST /post.php HTTP/1.0
  sockwrite -n $sockname Host: the-host.com
  sockwrite -n $sockname Content-Type: application/x-www-form-urlencoded
  sockwrite -n $sockname Content-Length: $len(%data)
  sockwrite -n $sockname

  var %i = 0,%num = $did([i]<dialog>[/i],[i]<id>[/i]).lines
  while (%i < %num) {
    inc %i
    sockwrite -n $sockname $did([i]<dialog>[/i],[i]<id>[/i],%i).text
  }

This only works if the dialog is still open when you sockwrite this stuff.
If the dialog is supposed to close before that, you'll have to store the contents of the edit somewhere (like in a hidden custum window) and then send it from there.

$input(Me like stars, You too?)