[HECnet] More NRT

[Paul Koning]

> On May 5, 2020, at 1:14 AM, Thomas DeBellis <tommytimesharing at gmail.com> wrote:
> 
> What's fun about the Tops-20 NRT client (SETHOST) is that it doesn't do much aside from parsing for an escape character and node name.  It builds a connection string and checks to make sure the remote system is either a 10 or a 20.  Then it twiddles a few things on the terminal (a few more if you're running my changes to handle page mode).  Finally, and this is the cool part, it issues an MTOPR% to directly connect the local user's terminal to the open DECnet connection (port 23).
> 
> Thereafter, the client does nothing until the interrupt character is typed or the connection is broken.  So response can be pretty snappy because you are never running in user space; no context switching.  The CTERM client on the other hand is reading and writing data and otherwise handling the specifics of the protocol in user space.  So, more overhead and more context switching.
> 
> As an experiment, I removed the checks for Tops-10 and Tops-20 and tried connecting to a few hosts on HECnet.
> 
> 	• Tops-20; TOMMYT and TWENEX worked (of course)
> 	• Tops-10; VENTI worked
> 	• RSX-11+; MIM accepted the connection and broke it as soon as I started typing. 
> 	• VMS; LEGATO accepted the connection and broke it as soon as I started typing.
> 	• RSTS; TRON accepted the connection and then did nothing.  It never broke the connection, but never displayed any banner or anything else.  It appeared hung.
> So it would appear that NRT servers only exist on the 36 bit line.  Perhaps it's possible to configure the service for other platforms?
> 
> The first few RSTS systems I tried didn't appear to be online; MEZZO, PLUTO, RSTSE and BITXOT.  The few Windows systems I checked didn't appear to be online, either; WXP, MISSY, KIBBEH and WATAN.  I'm not sure if that means they refused the connection attempt outright.

Try NI1D, user ID 100,100.  I just checked it and TRON, both correctly answer the RSTS remote terminal protocol.

Keep in mind that the NRT protocol is not actually one protocol, it's four protocols.  At connection setup this is sorted out, if the client side knows how to do that.  TOPS, VMS, RSX, and RSTS are the four flavors.  The "unsupported" remote terminal program on RSTS knows how to do this.  I don't know about the TOPS-20 version.

BTW, I just asked NI1D to connect to TWENEX, to verify its TOPS20 NRT implementation.  That works as expected.

	paul