[Info-vax] OpenVMS Virtual Terminals (was: Re: DECnet Phase IV broken after VSI update)

[Stephen Hoffman]

On 2021-10-31 12:59:22 +0000, Craig A. Berry said:


> There is also something called a virtual terminal (VTDRIVER?) but I've 
> never used it and couldn't find much in the way of documentation just 
> now.
> 
> As Hoff said else-thread:
> 
> "It'd be interesting to see if ssh could be adapted to permit VT 
> virtual terminal support, too."

VT Virtual Terminals are TTDRIVER, reconfigured and operating as 
disconnectable.

https://vmssoftware.com/docs/VSI_SYS_MGMT_MANUAL_VOL_I.PDF#page=270

Also see the DISCONNECT and CONNECT commands in DCL.

Getting DECterm to deal with this would be substantially more of an 
effort, with all of X along for that dark and scary and 
really-just-an-RPC-with-an-attached-windowing-system, ride.

Virtual Terminals are handy when connections are spotty, which used to 
be modems and now might be mobile or congested or other spotty network 
connections.

The closest client-side analog to the OpenVMS virtual terminal support 
is arguably the GNU screen and BSD tmux apps, though these must 
continue to be connected with the server and don't otherwise preserve 
the server-side session.

For server management, this virtual terminal support was a way to 
temporarily back out of a connection without losing context, 
fix/restart/rewire/reboot whatever happened with the connection or with 
client-side, and re-connect and resume the server session. Such as 
happens when the modem drops out. Yeah, modems, how quaint. Which is 
why virtual terminal support really hasn't seen much widespread use in 
recent decades.

Getting ssh and the rest over to its own terminal device name and off 
FT and/or BG would make the whole thing a shade easier to manage using 
traditional tools, too. Though I do recall somebody around here has 
grumbled once or twice about OpenVMS (dis)integration with IP. OpenVMS 
development had its head... elsewhere and too-long-preferred DECnet and 
OSI and for way too many years, and the fallout from that era continues 
to plague us.

Not that I expect any of this to change this decade, as VSI has other 
and higher-priority work.


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