New Telnet client for old DOS machines

Discussions on programming older machines

New Telnet client for old DOS machines

Postby Brutman » Mon Nov 30, 2009 9:18 pm

For the last two months I've been working on Telnet, and it is finally ready for testing.

The download link for the full set of TCP/IP apps can be found on http://www.brutman.com/mTCP . At the moment Telnet is not included with the other apps, so it has a separate download link on that page.

All of these programs should run really well on the oldest 8088 class machine you can find. I do all of my testing with a PCjr and an XT. One of the big challenges with a telnet client is good terminal emulation and screen updating performance. I think that you will be pleasantly surprised with this telnet client compared to other ones you might have used.

Give it a shot and let me know what you think ...

Mike
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Re: New Telnet client for old DOS machines

Postby Vorticon » Fri Dec 04, 2009 8:13 pm

I see that the requirements for running the telnet client are not exactly commonplace, but there is an alternative if you happen to have a Linux box. Linux allows you to connect a remote console via the PC's serial port and run an independent session that way, and so all one has to do (after some minor configuration on the Linux side) is to connect the PCjr via the serial port to the Linux box and use any terminal program (I used both Procomm and Comit Lite) to access an independent Linux session. From there, assuming that your Linux box is internet enabled, one can use telnet, ftp and Lynx on the PCjr in text mode of course.
I have doing that for a while on my TI 99/4A computer, and it works just as well on my PCjr (upgraded to 640K). As a matter of fact, I recently bought a bluetooth RS232 wireless cable with a range of up to 300feet that allows my PCjr which is living in my library to connect to my Linux box in the basement (2 stories down) with no physical cables.
If anyone here is interested in learning how to configure Linux to allow serial sessions, feel free to contact me and I'll be happy to provide you with the fairly basic instructions.

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Re: New Telnet client for old DOS machines

Postby Brutman » Sat Dec 05, 2009 7:40 am

Ah, but see any machine can be used as a terminal emulator through a serial port. I was doing that 25 years ago with my first PCjr, Procomm and a modem.

An Ethernet connected machine can telnet anywhere your network takes you. And it is far faster too .. The PCjr generally ran at a line rate of 2400 bps. If you went faster, you were subject to losing characters because of the keyboard interrupt design, slow screen updating, or diskette writes. Telnet is far far faster. Where a network connected Jr really shines is on FTP. My FTP transfer rates to a parallel port connected hard drive are around 20KB/sec. That is about 2x faster than what the floppy drive can transfer.

If all you are going to do is connect to your local Linux box anyway, then the network ability of telnet really isn't terribly useful. But I like the idea of the PCjr (or whatever machine I run Telnet on) being a standalone machine and a peer on the network, not as a 'dumb head' to the local Unix machine.

Take a look at the Xircom PE3-10BT. It connects to the parallel port (modified or regular), so installation is a breeze and it can be moved to other machines quickly. They used to be all over on eBay and they can still be had for reasonable prices.

The wireless RS232 is an option for where Ethernet wiring is not available. But then things slow down again. If the computer lab expands to a place with no wiring I'll be looking at that option.
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Other network apps?

Postby Brutman » Sat Dec 05, 2009 8:13 am

On a slightly different note ..

Do you have any ideas for other network apps that would be useful on an old machine?

I'm thinking of doing an NTP (Network Time Protocol) client next. I have machines that do not have a clock/calendar on them, so I'd like to put DHCP and an NTP program in AUTOEXEC.BAT so that I don't have to set the time by hand again. NTP could also be used to keep machines that do have a clock synced.

Mike
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Re: New Telnet client for old DOS machines

Postby Vorticon » Sat Dec 05, 2009 9:57 pm

I have been using baud rates of 19200 so far without any issues, and this is more than sufficient for telnet activity.
I mostly am interested in telnet so I can connect to BBS's out there, and I have a couple that I regularly visit.
I looked at the Xircom adapter, and it does not have a pass-through LPT port, which will be problematic for me since I rely heavily on my Zip drive as I only have one floppy drive (You wouldn't happen to have an expansion chassis for sale would you?). Besides, it looks like I will need a V20 upgrade to take advantage of your telnet software.
I have to admit though that it is pretty cool to be able to access the net directly from the PCjr, and NTP would be a great practical application.
Do you know a source for a clock/calendar card by any chance?

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Re: New Telnet client for old DOS machines

Postby Brutman » Sun Dec 06, 2009 7:43 am

I can't make my Jr run reliable over 9600, and even at 9600 the screen I/O has to be done very carefully. Keyboard activity during a file transfer is impossible - the machine uses NMI for deserializing the keyboard stream, and that takes longer than a byte will remain in the 8250 UART buffer. For interactive use like Telnet 19200 might work, but I'll bet that if you press a key while data is coming in you will lose bytes.

The Xircom doesn't have a pass through, but I have two parallel ports. :-) I thought that you had done the LPT2 modification - if you have not done it then go ahead - it's not that complicated.

None of my software requires a V20. My PCjr has a V20, but I also test on a stock PC XT with the original 8088. (Most of my testing for Telnet has been on the 8088 - I ran it for a few days while I was working, using it for IRC and doing real work on my Linux boxes.)

Clock and calendar usually came with an expansion chassis. I just saw a chassis on eBay .. keep your eyes out. There are two other alternatives - the Integrity Clock Cartridge and the Dallas Semiconductor DS1216E. I prefer the Dallas chip - it installs under a ROM chip on the motherboard and is basically transparent to the machine unless you run the software. Here is the link to the writeup: http://www.brutman.com/PCjr/DS1216E.html . The Integrity Clock Cartridge uses a related chip, but it requires a cartridge slot. I wrote new software for the cartridge so if you find one in the wild definitely grab it. (Here is a description of the clock cartridge - http://www.brutman.com/PCjr/pcjr_options.html#Integrity_Technology_Clock_Cartridge: . I need to post the software.)
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Re: New Telnet client for old DOS machines

Postby Vorticon » Sun Dec 06, 2009 9:12 pm

OK you got me fired :)
I located a Xircom parallel adapter on ebay and I made an offer for it. Asking price is $56 but I think I can get it for cheaper. I actually do have an extra printer port sidecar, so I will modify it for LPT2 and make it bidirectional per your excellent instructions, and this should solve my port problem.
I also bought a DS1216E chip and will add it to my system once I receive it.
I will let you know how everything turns out once the modifications are done and will give you feedback on your telnet client.
Heck, my PCjr is starting to look more like an XT...
By the way, are you programming straight in assembly or do you use a high level language with embedded assembly?

Walid
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Re: New Telnet client for old DOS machines

Postby Vorticon » Thu Dec 10, 2009 10:05 pm

Well, I got my Xircom adapter in today's mail, so I went ahead and modified my extra printer port sidecar for bidirectionality and LPT2 and it passed the test. However, I noticed that when I fired up the PCjR with the Xircom adapter connected to LPT2, then that port was not recognized. So what I ended up having to do was boot up without the adapter, then connect it afterward. Is that a common issue? It's really a minor inconvenience, but I always hate to plug anything on a live computer in general...
Since the adapter came bare with no power supply or drivers, I used a standard wall wart set at 12VDC and 300mA then located the appropriate packet driver on the net (PR3PD.COM). I connected the adapter to my router and I got a green light, and the packet driver was able to find it on LPT2. From there, it was a simple matter of following your directions on how to set up the configuration file (TCP.CFG) and setting up DHCP et voila! I was able to telnet as well as ftp straight from my PCjR!
Everything seems to work as it should, with the minor exception that telnet does not display any ANSI colors.
My hat is off to you Mike for this magnificent programming feat and it is amazing to me how much could be achieved with a computer never really designed for serious computing, or so did IBM think :)

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Re: New Telnet client for old DOS machines

Postby Brutman » Fri Dec 11, 2009 7:09 pm

Walid,

I have one parallel port adapter that I did the LPT2 modification to that does not show up regularly. All of the others show up. The BIOS of the machine scans for it, but my theory is that there is something flakey about the individual sidecar and it gets missed during the BIOS scan because it doesn't respond correctly. I'm not sure what the cause is, but it is definitely a nuisance.

My workaround is to go into debug and patch the address in by hand in the right location. My memory is fuzzy, but the BIOS area for COM ports and LPT ports starts around 0000:4000 in memory.

My Telnet program should display ANSI color - what kind of system are you connecting to? On Linux Fedora Core 2 (my outdated server box) the 'ls' command does color, as does VIM, Lynx, etc. It's probably a server side issue. Tell me the machine OS and we'll figure it out.

I'm glad you tried it out - from your previous notes I figured you would be on RS232 forever!


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Re: New Telnet client for old DOS machines

Postby Vorticon » Fri Dec 11, 2009 8:05 pm

I'm actually connecting to a BBS (thekeep.net) and I'm not sure on what OS it runs, but I will ask. My LPT2 board is always recognized as long as there is nothing connected to it at boot, then it works just fine afterward...

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