from the VSFTPD
FAQ :
Q) Help! Can I change the port that vsftpd runs on?
A1) Yes. If you are running vsftpd in standalone mode, use the "listen_port"
directive in vsftpd.conf.
A2) Yes. If you are running vsftpd from an inetd or xinetd program, this
becomes an inetd or xinetd problem. You must change the inetd or xinetd
configuration files (perhaps /etc/inetd.conf or /etc/xinetd.d/vsftpd)