I've installed tftpd-hpa server from standard UM repository on my desktop UM 18.04.
While testing installation with local tftp client (tftp-hpa) I've stumbled upon the problem. Namely, tftpd-hpa accepts uploads and creates target files of zero length.
on serverA, installed tftpd-hpa, created /srv/tftp, added debian.iso in there. Adjusted options like yours in the config file, chown tftp:tftp /srv/tftp, restarted tftpd.
On client, installed tftp-hpa, then tftp serverA, get debian.iso, it brought it in.
Thank you for your reply!
Permissions were fine. I 'chowned' default /var/lib/tftpboot directory.
Just to be unambiguous: downloads work (i.e. get <file> client command) and uploads (i.e. put <file>client command) are problematic.