I have an installation of busybox on an embedded linux system that comes with a great little utility called rx:


Receive a file using the xmodem protocol

This is perfect for transferring files from a PC to the embedded system via the serial terminal. However, I'm also looking to transfer in the opposite direction. I couldn't find a complementary 'tx' utility. Does one exist?

  • It's been a while since I used that command. I don't recall the exact details anymore. I seem to recall that there were three different protocols each designed for pretty much the same purpose, and each of them had one program to send and one program to receive. If my memory serves me well, you can use sx to send and rx to receive. (And the other two protocols might have been named y and z rather than x.) – kasperd Feb 25 '15 at 0:31

Wow, that has to be the first time this century that I've heard rx referred to as a "great little utility"! :-) Yet we can still dust the cobwebs off those old commands.

  • XMODEM: rx for receiving, sx for sending.
  • YMODEM: rb for receiving, sb for sending.
  • ZMODEM: rz for reveiving, sz for sending.
  • Thanks for the answer. Unfortunately BusyBox does not have sx! This seems surprising to me since it has rx. BusyBox documents – user104387 Feb 25 '15 at 17:09
  • 2
    I see. Well, I guess that does make some sense since xmodem (and TFTP for that matter) is usually used these days as a last-resort file transfer protocol to load the next stage in a bootloader or update low-level firmware or things like that. Once the system is up and running (bootloader finished its job, firmware running sucessfully, etc...) one usually expects that a "better" file transfer protocol is available. – Celada Feb 25 '15 at 19:43
  • Where can we get these tools today? – not2qubit Jul 11 '19 at 17:55

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