The Apache FTP Server is a 100% pure Java FTP server. It's designed to be
a complete and portable FTP server engine solution based on currently
available open protocols. FtpServer can be run standalone as a Windows
service of Unix/Linux daemon, or as embedded into a Java application.
The default network support is based on Apache MINA, a high performance
asyncronous IO library.
It is also a FTP application platform. We have developed a Java API to let
you write Java code to process FTP event notifications that we call the Ftplet
API. Apache FtpServer provides an implementation of FTP server to support
this API.