which cassandra version does ctop support

[ajaxhe]

After I build ctop, and run it, I couldn't get the column family metrics.
Then, I review the source code, I found the mx4j http request is like below:
http://host:8081/getattribute?objectname=org.apache.cassandra.db:type=ColumnFamilies,keyspace=keyspac e1,columnfamily=standard1&attribute=ReadCount&format=long&template=identity

I copy the http url in browser, only
<?xml version="1.0" encoding="UTF-8"?>
retured.

I use cassandra 2.2.7, does it my cassandra version is too old?
Is the mx4j interface is changed?

I would very much appreciate any help or guidance you are able to give me.
thanks~