Install vsftpd

''sudo apt update && sudo apt install vsftpd''

Once installed check status

''● vsftpd.service - vsftpd FTP server
     Loaded: loaded (/lib/systemd/system/vsftpd.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2020-04-27 19:35:30 IST; 13s ago
   Main PID: 54532 (vsftpd)
      Tasks: 1 (limit: 1137)
     Memory: 652.0K
     CGroup: /system.slice/vsftpd.service
             └─54532 /usr/sbin/vsftpd /etc/vsftpd.conf
 
Apr 27 19:35:30 ubuntu systemd[1]: Starting vsftpd FTP server...
Apr 27 19:35:30 ubuntu systemd[1]: Started vsftpd FTP server.''

Congigue Firewall

''sudo ufw allow 20/tcp''