I would not be surprised if there was an implementation of MEX or IMP? For
N* with CP/M, don't know about N*Dos. ISTR that 99% of the code is the same
for all systems, just the overlay for the communications ports differed.
There's also Kermit :) a great fallback to have around.
And ISTR there was a configurable
XMODEM.COM out there for CP/M