Ultrix-11 Networking

Douglas Taylor dj.taylor4 at comcast.net
Sun Aug 29 12:41:28 CDT 2021

On 8/28/2021 6:19 PM, Bill Gunshannon via cctech wrote:
> On 8/28/21 4:13 PM, Douglas Taylor via cctalk wrote:
>> On 8/28/2021 1:15 PM, Bill Gunshannon via cctalk wrote:
>>> On 8/28/21 1:03 PM, Douglas Taylor via cctalk wrote:
>>>> Yes, I did create a new kernel and copy it to the correct place and 
>>>> chmod 644 the new unix file.
>>> Did yo have fun playing with the overlays?  :-)
>> I don't know what this means.  The kernel creation was automatic, it 
>> seemed to check for enough room.
> I guess you did the bare minimum to get the network up.  When I buld
> a new kernel I tend to add all the devices (like multiple network cards
> and serial cards) that I may want in the future.  I have often had to
> manually shift things around and usually create one or two additional
> overlays to get it all to fit.  I actually enjoy doing it.  :-)
I had only toyed with the idea of adding a dzv11 so real terminals could 
be connected to a real pdp11 Ultrix-11 system.  I guess I'll find out 
once I get there.
>>>> On my Debian system I can install ftpd and telnetd (they are still 
>>>> in the Debian package list) which are the unsecure ones, but I 
>>>> don't know how to configure them or start them.  As in, # systemctl 
>>>> restart ftpd
>>> Probably easier to turn them on on Ultrix-11.  Just modify inetd.conf.
>>> Actually, I just looked and ftp is on by default. Telnet is not.
>> I edited inetd.conf to uncomment telnet.  It helped.
>>>> It turns out to not be a hot topic: "How do I make my Liinux system 
>>>> less secure?",  but for us that noodle around with old computers 
>>>> with obsolete operating systems it is exactly what we need.  In the 
>>>> past I remember using Filezilla to go from a Windows7 machine into 
>>>> a Vax without any problem.
>>> I suspect you will be somewhat disappointed with networking in
>>> Ultrix-11.  Not that there is something wrong with it, just that
>>> the hardware is nothing like you are used to.  In the early days
>>> of networking it was not unusual for systems like the PDP-11 to
>>> crash just because of the traffic passing by on their network
>>> connection.  The advent of switches helped alleviate that but it
>>> is still common to crash a system by pushing data at it from a
>>> modern ftp.  I expect FileZila will do it.  To be honest, I always
>>> preferred Kermit for moving files.  It is possible to keep packet
>>> sizes down and even slow down the transfer rate to give the PDP
>>> time to handle it.
>>> bill
>> I brought up a Vax Alpha 3000-300 and tried interacting with the 
>> Ultrix-11 simulation:
>> Starting in Ultrix-11 I could log into the vax via telnet. Ultrix-11 
>> ftp was able to transfer a short ascii file from the Vax to the 
>> Ultrix-11 sim.
> Just another note. remember that ulimit is only 1024 on Ultrix-11 by
> default.  That means no file larger than 10M.  Unless you raise ulimit.
>> Going the other way, Ultrix-11 would reject an ftp request from the 
>> vax, here is the error message -
>> $ ftp
>> %TCPIP-E-FTP_NETERR, I/O error on network device
>> -SYSTEM-F-UNREACHABLE, remote node is not currently reachable
>> $
> Been a long time.  Could have to do with PTYs.  Remember, FTP takes two
> open connection and the number of possible connection on Ultrix-11 is
> very limited.

I think I noticed that I only had 2 PTY's during the install/kernel 
process.  Glad you mentioned this, it had gone over my head.

Ignore the VAX error, the error was mine.  I typed the ip wrong, should 
have been, not  Blame it on bad eyes, old 
age, small font, clumsy fingers.

>> Ultrix-11 would allow a telnet connection (after the change to 
>> inetd.conf) and I could do an ls, but when I asked for a man page it 
>> hung up.  Nothing after that, had to kill it.
> I told you it was very unstable.  :-)
>> I got the same result whether I was telneting in from the Vax or 
>> Linux computer.  Probably not news to you.  I wonder if real hardware 
>> works just like this....
> Sometimes, but I always found SIMH less reliable with my limited use
> of it.  I always preferred real hardware.
>> It was good to find out that you can get things in/out of the 
>> Ultrix-11 simulation.
> Like I said, I usually find Kermit over emulated serial lines to be more
> efficient at moving stuff on and off.  The network may be faster but
> failures after 4 hours of a transfer can be very frustrating. Better
> to let kkermit have it over night and then get a fresh start in the 
> morning.
> bill

More information about the cctalk mailing list