Subj : Solved issue with SyncTerm after up/download on my BBS
To   : Digital Man
From : AKAcastor
Date : Wed Apr 17 2024 12:55 pm

 > Solution:
 >
 > The telnet IAC handler in DOSBox-X softmodem.cpp was modified to deny
 > requests to disable binary mode, and in case a 
 > client disables binary mode a
 > request to enter binary mode is sent.

 DM> This sounds like a hacky-work-around and not a 'fix'.

I don't disagree with that, but then also I consider running modem-based DOS software inside DOSBox with telnet emulation a bit of a hacky work around in the first place, so it doesn't really offend my sensibilities.  ;)

 DM> If ASCII (non-binary-tx) mode is negotiated succesfully 
 DM> when SyncTERM first connects to telnet server, then it 
 DM> should be free to return to ASCII mode later.

ASCII mode was never negotiated successfully, the session was in binary mode from the beginning.  SyncTerm is incorrectly 'returning' to ASCII mode after file transfers.

I don't think I see a pressing need for my system to support ASCII mode telnet as I expect any client should support binary mode.  (maybe there's some edge cases in niche implementations or a benefit of ASCII mode that I am missing?)

 DM> It just sounds like there's a bug in the DOSBOX-X 
 DM> terminal server with tracking the remote and/or local 
 DM> "BINARY TX" state and that needs to be fixed rather 
 DM> than just blindly rejecting requests to exit binary 
 DM> transmission mode.

 DM> Maybe you would have had better luck with DOSBOX-
 DM> staging instead of of DOSBOX-X?

I agree there is likely a bug hiding in the telnet emulation, I may dig deeper for it yet.  In the meantime, convincing SyncTerm to stop switching to ASCII modes removes the issue from my system.

Telnet emulation in DOSBox-Staging is broken also.  I don't know if it has the
same behaviour with ASCII vs binary mode but it has other telnet protocol bugs,
like sending binary data from DOSBox does not escape the IAC bytes.  (due to
this binary transfers work when DOSBox is receiving, but not when sending)

I haven't ruled out DOSBox-Staging in the long term, but DOSBox-X has been
working well for me and I have already been patching it to suit my needs
(mostly a bit of cleanup/hackjobs in softmodem.cpp).  Eventually I hope to get the softmodem code cleaned up enough to submit to the github project.


Chris/akacastor
                              

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 * Origin: Another Millennium - Canada - another.tel (21:1/162)

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