You are looking in the right way, just missing a little thing :
it's : 'LDAP://st8en1.dhw.zain.com.st/rootDSE'
This will result in :
Select AdsPath, samAccountName, GroupType from 'LDAP://"+GetObject("LDAP://st8en1.dhw.zain.com.st/rootDSE").Get("defaultNamingContext")+"' "+$filter

In case it's not working (don't see why, but everything can happen), replace "st8en1.dhw.zain.com.st" with the server netbios name.

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? getobject(Kixtart.org.Signature)