* @return url of passport login server
*/
private static String getPassportLoginServer(ProxyInfo info) throws IOException
{
HamsamHttpsConnection conn = new HamsamHttpsConnection("https://nexus.passport.com/rdr/pprdr.asp", info);
conn.doRequest();
String header = conn.getHeaderField("PassportURLs");
int start = header.indexOf("DALogin=") + 8;
int end = header.indexOf(',', start);
return "https://" + header.substring(start, end);
}