I have a Ubuntu 16.04 server running vsftpd and I can connect from Filezilla Client on a Windows PC on port 21.
I would like to change the port number so I have edited /ect/vsftpd.conf and set ftp_data_port=1233 and listen_port=1234. I've amended the port redirection rules on my router to redirect incoming WAN on 1234 to my IP Ubuntu server address on 1234.
Filezilla connects but won't display a directory listing. Get message "Server sent passive reply with unroutable address. Using server address instead."