static void setHeaders(URLConnection con) throws IOException {
  ifndef NoComputerID
  String computerID = getComputerID_quick();
  if (computerID != null) try {
    con.setRequestProperty("X-ComputerID", computerID);
    con.setRequestProperty("X-OS", System.getProperty("os.name") + " " + System.getProperty("os.version"));
  } catch (Throwable e) {
    //printShortException(e);
  }
  endifndef
}