Package lrzsz

The lrz and lsz modem communications programs

http://www.ohse.de/uwe/software/lrzsz.html

Lrzsz (consisting of lrz and lsz) is a cosmetically modified
zmodem/ymodem/xmodem package built from the public-domain version of
the rzsz package. Lrzsz was created to provide a working GNU
copylefted Zmodem solution for Linux systems.

General Commands (Section 1)
rz
This program uses error correcting protocols to receive files over a dial-in serial port from a variety of programs running under PC-DOS, CP/M, Unix, and other...
sz
Sz uses the ZMODEM, YMODEM or XMODEM error correcting protocol to send one or more files over a dial-in serial port to a variety of programs running under...