Telnet session: cannot disable BINARY negotiation; login fails against Ultrix telnetd (Enter key handling)
Telnet session: cannot disable BINARY negotiation; login fails against Ultrix telnetd (Enter key handling)
1 vote
Product: Remote Desktop Manager (Windows), version 2026.3.8.0 64 bit (PreJIT)
Session type: Telnet, embedded (tabbed)
Server: DEC Ultrix 4.5 (VAX) telnetd
Problem Login through the RDM Telnet session always fails, or hangs, on Ultrix telnetd. The same server works fine from PuTTY in Telnet mode.
What a packet capture shows
- RDM proposes IAC WILL BINARY and IAC DO BINARY, and the server accepts both.
- With "Return key sends a new line instead of a carriage return" ticked, Enter is sent as CR LF (0d 0a). With it unticked, Enter is sent as a bare CR (0d).
- A bare CR leaves login stuck after the username: no Password: prompt.
- CR LF reaches the Password: prompt, but login then reports "Login incorrect" with the correct password.
Analysis
Once BINARY is active, BSD-derived telnetd (including Ultrix) turns off CR/LF translation. The CR in CR LF then stays inside the line, so login receives "username<CR>" and "password<CR>" instead of the clean strings. The server also stops adding CRs on output. This is consistent with what the capture shows. I have not found an option to turn off BINARY, or to send LF only for Enter. Remapping Enter to another CTRL-J in the Keyboard tab had no effect on the bytes sent.
Requests
1. A per-entry option to disable telnet BINARY negotiation (or make it opt-in).
2. Or an Enter-key option to send LF only, or CR NUL, that is honoured for keyboard input and for the autologin (User/Password prompt string) feature.
3. Ensure the Keyboard tab key map is applied to Enter in Telnet sessions.
All Comments (3)
Hello,
Thank you for the request, I've opened an internal ticket and we'll take a look at what we can do.
Regards,
Hubert Mireault
Hello,
Thank you for your patience while our team looked into the issue you reported.
I'm happy to let you know that the latest version of Remote Desktop Manager (2026.3.16.0) includes the requested feature. You can download it from our website here:
https://devolutions.net/remote-desktop-manager/download/
Once you have installed the update, could you please test it in your environment and confirm that everything now works as expected? If the issue persists or if you notice anything unusual related to the same original problem, just reply to this message with a few details, and we will be glad to look into it further.
Thank you for your collaboration.
Best regards,
Maxim Robert
Thanks, Maxim - confirmed. With RDM 2026.3.16.0 the Telnet session works against ULTRIX 4.5, on both a real MicroVAX II and a SIMH-emulated one, including autologin. I’ve moved my VAX entries from PuTTY to native RDM Telnet entries.
I also checked the session on the wire: neither RDM nor the ULTRIX telnetd negotiates BINARY any more, so the server stays in NVT mode and CR / CR LF are handled as expected.
Kind regards and many thanks.
Mark Usher