I am trying to get metadata for all objects using Partner API, 

got some samples in internet for calling binding .describeGlobal();

but when I am calling describeGlobal  its expecting   SessionHeader, CallOptions, PakageVersions[]

also there is no URL property for my binding object , and If I pass nulls for binding .describeGlobal(); instead of parameters, Giving following exception

UNKNOWN_EXCEPTION: Destination URL not reset. The URL returned from login must be set in the SforceService

Please somebody give me a code snippet to get Metada for all objects using partner API, I wanna use partner API because I want my code to work for any organization without any change.

I am trying to get metadata for all objects using Partner API, 

got some samples in internet for calling binding .describeGlobal();

but when I am calling describeGlobal  its expecting   SessionHeader, CallOptions, PakageVersions[]

also there is no URL property for my binding object , and If I pass nulls for binding .describeGlobal(); instead of parameters, Giving following exception

UNKNOWN_EXCEPTION: Destination URL not reset. The URL returned from login must be set in the SforceService

Please somebody give me a code snippet to get Metada for all objects using partner API, I wanna use partner API because I want my code to work for any organization without any change.