I haven't heard of the Fxp protocol. The Ftp protocol used to be supported in the sun.net package but I believe this is no longer distributed starting with JDK 1.4. In any case Sun advises that the sun. packages should never be used as they are unsupported and can be removed from the JDK without notice.
There are several
Java FTP components available online. In fact my company JSCAPE provides such a component in its iNet Factory product.
Could you explain more about your requirements. I would be happy to help point you in the right direction.
Thanks,