vsftpd client reports CLOSEWAIT

Dear all,
I built a new ftp server (vsftp) for remote clients (loggers - quite old conception) and these report CLOSEWAIT connections. On server side, all is correct in logs.

Here my cnf:

anonymous_enable=NO
local_enable=YES
write_enable=YES
local_umask=022
dirmessage_enable=YES
connect_from_port_20=YES
chroot_local_user=YES
allow_writeable_chroot=YES
listen=YES
listen_ipv6=NO
pasv_min_port=50000
pasv_max_port=50100
userlist_file=/etc/vsftpd/user_list
userlist_deny=NO
pam_service_name=vsftpd
userlist_enable=YES
dual_log_enable=YES
xferlog_enable=YES
xferlog_file=/var/log/xferlog
vsftpd_log_file= /var/log/vsftpd.log

Please see attached log from client .
Regards,
Jacques