service instance initialization fails using session cookie

String session = "vmware_soap_session=\"" + sessionCookie + "\"";

si = new ServiceInstance (new URL(serviceUrl), session, true);

the above call returns si as null always

so ,i am using other constructor

si = new ServiceInstance(new URL(VCENTER_SDK),username, password, true);

Is there any other way where i can get the username,password and the VC IP without service instance from the mob,like when we are loggedin into webclient,can we get the vc creds and vc ip from session?

Please point me to the sample