Zmodem is a good protocol. Back in the pre-internet days I used to spend hours breathlessly watching warez transferring at 300 baud over my modem from some Apple ][ site. Things got a lot more reliable with the xmodem protocol and, later, zmodem. Checksums! Block resends! Resuming midstream! Amazing.
I still use zmodem on occasion to transfer files from my Windows laptop to my Linux server. With all the firewalls and security crap it's a lot of effort to do a proper TCP/IP file transfer, but all I need is an open terminal session and rz/sz and I'm set.