Querying license information of Esx connected through vCenter

I am validating license information of a Esx Server to find out whether a server is in Evaluvation. When connecting to a Esx server directly and taking License information either from "ServiceContent.licenseManager" or from "HostSystem" object both works correctly. But when I try to get the same information for an Esx connected through vCenter - the "HostSystem" object contains other information intact, but not the license information. License information is null.

I am using the C++ wrapper from the following link https://github.com/bfzhao/Native-vShpere. Can someone tell me if I have to query the license info of the host through some other means when an Esx is connected through VC? vSphere SDK is 5.0.