Hi Furquan,
do you use the classical REST interface to send your XQuery expressions to the server? In that case, you could either check out the logging facilities by the applied web server (possibly Jetty) or play around with another proxy like nginx [1].
You will be more flexible by using RESTXQ [2] and writing server-side XQuery code. The XQuery Module [3] or the Client Module [4] can be used to evaluate the received query.
Hope this helps (and thanks for writing to the mailing list), Christian
[1] http://nginx.org/ [2] http://docs.basex.org/wiki/RESTXQ [3] http://docs.basex.org/wiki/XQuery_Module [4] http://docs.basex.org/wiki/Client_Module