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Z modem Upload - Printable Version

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+---- Thread: Z modem Upload (/showthread.php?tid=898)



Z modem Upload - Debyl - 04-22-2022

I cannot get the Z modem upload to work.  Using Banana Com, Telemate or Connex;  the upload reaches 100% and then restarts again from 0%.  It does not finish.  Has anyone had any luck with file uploading?

Kermit seems to work, but is way too slow to be practical.

I am using an IBM PC (486 DX4-100 cpu).

Thank you,
Lucas


RE: Z modem Upload - admin - 04-23-2022

I use Zmodem with the Amiga and Windows 10 all of the time for moving files between the systems. I also do this with the C64 and the Amiga or PC.

I just fixed an issue that might help your Zmodem transfers. You can type AT*UPDATE to update the WiModem232 firmware.

The problem with file transfer protocols is that they were created for land lines with fixed maximum latency. With a land line there is a direct peer to peer connection. With a WiFi modem, there is a WiFi connection to your router, and from your router to ISP, and ISP to where ever your connection point is, and back. Land line latency across the planet is about 50ms max. WiFi latency (known as PING TIME) can be several hundred milliseconds, which is too long for Zmodem. There are some protocols with very long time out windows (several seconds), and all of those work just fine. If you can tweak the timing of your Zmodem protocol (which is possible with some systems that load the protocol as an external module), you can increase the ACK delay window time and make Zmodem work in the worst case scenarios. You just have to have a version where you can do that.

Update the firmware - I made the change just a few days ago - and try it again.


RE: Z modem Upload - ThrakaAndy - 05-26-2022

I'm having the same issue, latest firmware. Two different computers, one 486 33dx and another 486 50dx. Couple different clients too, never works. I'm also used to a bbs client detecting an upload request with zmodem and popping up the upload dialog, but that doesn't trigger either. When I force it to upload (generally the PGUP key) and select the file, it just never goes through correctly and always fails. I've setup my own BBS too (synchronet) and verified I can upload to it just fine with syncterm on a modern computer.


RE: Z modem Upload - admin - 05-30-2022

This all boils down to latency of your router and ISP, things that Zmodem never had to deal with when using a direct (phone line or cable) connection. You have to be able to tweak the Zmodem internal settings, or you have to use a different protocol. There is nothing that can be done about the over-air latency caused by a WiFi connection.


RE: Z modem Upload - ThrakaAndy - 06-01-2022

Thank you for the response. I'm curious, why wouldn't it at least work on my LAN? I have a synchronet and mystic BBS running locally, connected to the router via a cable (so no wifi on the server) and it still isn't working. However, syncterm via telnet works fine to my LAN BBS and using zmodem.


RE: Z modem Upload - admin - 06-01-2022

If you are using using Telnet (real Telnet) then you would have to make sure that you are using Telnet with the WiModem. If you don't have matching modes (RAW or TELNET) on each end, you will never get file transfers to work (any protocol). It could be that there is enough latency with your LAN to cause the problem. Stock Zmodem requires <25ms of latency on packet ACKs. You could trying PINGING the WiModem through the LAN and seeing how much latency you have.