I have installed hub correctly and set the XML-RPC protocol usable,but when I click hub->settings,it tells me that:The XML-RPC extension is not enabled on the server. You can not manage your hub until this extension is enabled.
How can I do?
Depending on your server you would search something like "Enable XML-RPC PHP5 Ubuntu". This is outside of Moodle and on the actual server. It cannot be done inside of Moodle.
Yes you need to install xmp-rpc for php. It is one of the "recommended" but not required php configurations when you install Moodle. Info on how to install / set it up is here:
http://docs.moodle.org/26/en/admin/environment/php_extension/xmlrpc