The RV Config API provides an OOTB way to retrieve the subscriptions of a specific client:

ClientTransport.getSubscriptions()

However, the result returned by this API only includes the first page of subscriptions. If the list spans more than one page, the subscriptions on the remaining pages are not available. Attached is a simple Java program (Filename: GetRvdClientSubjects.java) which can be used to get the full subjects list of all the clients for the specified RV(R)D HTTP interface URL. It does not use the RV config API. To be able to run it you will need to include a third-party open source Java HTML Parser jsoup (http://jsoup.org/) in your classpath.

usage: java GetRvdClientSubjects
             -basedUrl <url> // Rvd or Rvrd HTTP interface URL, such as http://localhost:7580
             -outputDir <dir> //directory path to which the files containing subjects for each client will be written to

Note: Use jsoup version 1.7.2 as we found the code does not work properly with later versions of jsoup.