The best replacement for xmodem is ymodem.

The best alternatives to xmodem are rated as following:
★★★★★  ymodem
★★★★  xmodem 1k
★★  zmodem
★★  kermit
★★  tftp
★  xmodem-1k

Your alternative for xmodem is not listed? Suggest!
Speaking about xmodem, one probably shouldn't forget about putty.

Other search terms related to xmodem and their ratings are:
★★★★★ putty
★★★ minicom
★★ teraterm
You have in mind a companion for xmodem and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of xmodem in all years. Click on graph for more.
xmodem
ymodem
xmodem 1k