serial connection magic

[pjungwirth]

I already typed this once and then lost it, so here is the short version:

I was recently working on a Sun 450 that had no keyboard or monitor. Instead, it was connected by a null modem cable to an NT machine, and you could log in via Tera Term on COM1. At one point, this machine totally locked up. Telnet sessions from remote machines froze, all IP traffic ceased, you couldn't ping the box (although the network connection showed a light), and nothing was going on at the serial terminal. It was obviously more than just a network problem.

The reason the computer lacked a monitor is that it was inside a small networking closet. Since the company was moving into a new office space, there was a woman from Verizon working on the networking cables plus some other guys setting up a massive UPS that would power the whole floor. So *anything* could have happened.

And there I was with a running box but no input and no output. I tried closing the serial terminal and reopening it, but I just got a blank screen. Pushing enter resulted in this:

{3}ok

Whatever that means.

I was very concerned that I would have to flip the switch, wrecking havoc on the filesystem. Then someone suggested I type "go" into the serial terminal. Shockingly, that restored the connection. I had a login prompt! From there I was able to safely reboot the machine, and everything seemed fine.

"go"?! What in the world? Has anyone heard of this before? What exactly does that do? Re-initialize the connection somehow? All I have to say is Weird. . . . If only all computer troubleshooting were that simple. Don't you just wish you could yell or type "go" and your computer would start working again? Blue screen of death? No problem! "Go!"

Paul
~{:-)

[Paleo Pete]

I'm not absolutely positive, but I think it's using BASIC or a form of it. The OK is a standard BASIC prompt, (the {3} part is strange, usually it just says OK with a blinking cursor, unless that's a typo...) GO probably runs a program or batch file named, of course, GO.BAS. Filenames with the BAS extension are usually the ones run by BASIC. If it is BASIC, it can also be used for programming, if you can find a book on using BASIC. It was one of the first programming languages, and is still used fairly often, although others have taken the front seat long ago.

Later GWBasic was released, QBasic, BASICA, and from there others became more popular. C++, COBOL, FORTRAN, PASCAL and others I think. Check Google for programming, you might turn up some interesting reading. (I decided not to run a search myself because every time I do I end up reading for an hour or two and neglecting what I'm here to do...and that's certain to be a fascinating topic, I'd be here all night...) http://www.PCGuide.com/ubb/biggrin.gif

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[pjungwirth]

Thanks Pete for your reply. My very first programming experience was BASIC on a Tandy 1000. I still remember my friend trying to vain to get me to understand a for/next loop, the epiphany of the implications of GOSUB (I'd been using--what else?--GOTO), and all the hours spent typing in programs by hand out of magazines. Those were the days! I think the Tandy had a specialized version of GWBasic. It was one of the only PCs at the time to support three-voice music (!), so the PLAY command had some non-standard syntax. Whenever I tried my games on friends' computers, I had to REM those lines.

Was BASIC ever used on Solaris machines, or just DOS? I doubt my problem in this case was BASIC; it seems to be something unique to serial connections. First of all, I never started an interpreter. Second, if I were in an interpreter, it would only run GO.BAS if I typed "RUN GO," not just "GO." Third, why would a BASIC program give me a UNIX login prompt?

Basically, the machine was totally frozen--I couldn't even ping it--until I typed "go" at this terminal window. Then I got a few messages (I don't recall what) and a login prompt.

I think the {3} may have referred to the runlevel? After I dropped the machine to runlevel 0, but before I rebooted, pressing enter at the terminal give this response:

{0}ok

I really think this was a serial-specific hardware thing.

Paul
~{:-)

[Paleo Pete]

Yeah, you're right, you would have had to type "RUN GO" if it were BASIC, I forgot about that. Maybe it's something peculiar to UNIX, I don't know, never used it at all...or could be, as you suggested, something related to serial connections, again I'm outside my range of knowledge. I just thought it might be BASIC because of the OK prompt, which is about 2/3 of my knowledge of programming...and BASIC...

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