From: https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/com.ibm.zos.v2r1.cs3cod0/ftp227-02.htm

The server received the PASV subcommand. The server successfully entered passive mode and 
is listening on the socket indicated by 
h1,h2,h3,h4,p1,p2, where h1-h4 are the host IP address 
and p1,p2 are the port number.

http://filezilla-project.org/

Welcome to the homepage of FileZilla, the free FTP solution. Both a client and a server are available. FileZilla is open source software distributed free of charge under the terms of the GNU General Public License

http://cyberduck.ch/

http://www.ilovefreesoftware.com/09/featured/4-best-free-ftp-software.html

http://www.ilovefreesoftware.com/29/windows/internet/download-free-ftp-client-core-ftp.html