Hayes command set history: The tech that dialed in a million modems

https://tedium.co/2023/02/22/early-modem-technology-history/

by ohjeez • 3 years ago

80 27 3 years ago

joezydeco3• 3 years ago

The AT command set is very much alive and well. All those cellular chips in your smartphones and IoT devices still communicate with their host processors over a serial communication line, identical to the Hayes box back in 1978.

The commands have gotten more complicated, but as far as I know ATI will still give you a typical part identification code.

mocko• 3 years ago

It truly is. For an example look at these guys juggling AT commands to control 5G modems fresh off the production line - https://forums.whirlpool.net.au/archive/3vx1k1r3-39.

Nextgrid• 3 years ago

Qualcomm (and maybe others) have alternatives though such as QMI.

joezydeco3• 3 years ago

I'm figuring that Apple has probably developed their own as well.

tyingq• 3 years ago

I like this old summary of various ways to trick a modem connected server into outputting +++ATH0, which would disconnect it.

https://opennet.ru/base/usersoft/3.txt.html

It did work on some modems with loose requirements around the timing and pauses.

tonyarkles• 3 years ago

Heh, I was one of the first in my group of friends to get DSL and the ping trick was a wonderful way to troll people. Before the DSL line, I too had a modem that was vulnerable so trying to send the ping would kick me off instead of the target.

rchowe• 3 years ago

It’s because Hayes held the patent on the modem having to pause for one second before it could receive commands.

Other modem manufacturers implemented the “time-independent escape sequence” to get around the patent[0]… the only issue being binaries that contained control codes and meddlesome kids.

[0] https://en.m.wikipedia.org/wiki/Time_Independent_Escape_Sequ...

hrunt2• 3 years ago

One of my first jobs was working for a mom-and-pop dial-up ISP. I persuaded my mom to get an account with them when I saw them in a computer magazine. I did not even have a web browser! A little after that, they hired me.

One of the things we used to do when I first started was shuck modems. We would buy the consumer models, break open the plastic cases, pull the circuit boards out, and slide them into slots of custom enclosures. Then we would hand-assemble DB-to-ethernet adapters and plug them into serial controller banks.

We bought any and all modems, but the cheap models from US Robotics and Supra were really a game changer. The only tough part was that dealing with the slight differences in command differences on the client side needed to connect to the different modem types.

ghaff3• 3 years ago

There was a period when various modem manufacturers were pushing speed limits and they did some non-standard things to do so. As I recall, USR's 9600 bps was one of the more non (Hayes) standard. Since you mention ISPs though, this was probably a bit earlier.

bhauer2• 3 years ago

You might be right about the USR 9600 bps mode, but for certain their original 14.4k bps mode was proprietary and named "HST." I still fondly remember when I got my Courier HST and witnessed its intense speed boost versus my prior 2400 bps modem.

hrunt2• 3 years ago

Yeah, but there were definitely incompatibilities with every speed increase. When 28.8k modems were coming out, the spec was not set yet, so several vendors released early versions (anyone remember v.fast?) and then updated the modem firmware later when the standard was set. And then when 56.6k modems came along, USR had X2 and Motorola and others had K56flex. About a year later, v.90 and v.92 came along to standardize everything.

If you were an ISP, you had to support everything. For the 56.6k stuff, I remember us having two separate dial-in pools for X2 and K56flex.

rasz• 3 years ago

USR had HST (High Speed Transfer), but the king was Telebit with TrailBlazer utilizing PEP (Packetized Ensemble Protocol). https://en.wikipedia.org/wiki/Telebit#PEP_and_the_TrailBlaze...

Supra on the other hand offered ridiculous discounts

"A manufacturer that disappeared leaving a trace in the industry Supra where cheap modems were sold in large quantities even in Akihabara" 2/3 https://ascii-jp.translate.goog/elem/000/001/425/1425488/ind...

Smartmodem 2400 had dropped in price to around $500 in 1987, but was still an expensive product. In 1987, Supra Corporation launched the SupraModem 2400, which is fully compatible with the Smartmodem 2400, for just $179.

asah• 3 years ago

LOL, a lot more than 1 million... more like 100M+

netsharc• 3 years ago

Somewhat related to AT commands, there's a collection of anecdotes from Linus Torvalds' old officemate in Uni Helsinki, one time Linus had a brainfart while trying to dial into his ISP, the result of which was that his harddisk bootsector ended up beginning with the string "ATDT " and his ISP's phone number. The next day Linus implemented permission controls.

Sadly DDG and Google can't find me anything with those keywords. Either that story has disappeared off the web, or search engines really suck nowadays.

Edit: Well, I found it, but I had to go to a blog where the story was quoted, and the blog author had written down the link not as a hyperlink: https://liw.fi/linux-anecdotes/

nico• 3 years ago

Either that story has disappeared off the web, or search engines really suck nowadays.

Given you found the story, it seems like it hadn’t disappeared off the web. However, search engines might suck.

hulitu• 3 years ago

If we play our cards right, the Linux penguin could be the next mass-consumer hit product. Can you imagine a Windows flag competing against our penguin?

dezgeg• 3 years ago

Hmm, there is a different 'accidental hard drive dialing' story in his autobiography (Just for Fun) - where that happened in Minix and as a result Linus chose to move to Linux full-time:

But in December, I mistakenly auto-dialed my hard disk instead of my modem. I was trying to auto-dial /dev/tty1, which is the serial line. But by mistake I auto-dialed /dev/hda1, which is the hard disk device. The end result was that I inadvertently overwrote some of the most critical parts of the of the partition where I had Minix. Yes, that meant I couldn’t boot Minix anymore. > That was the point where I had a decision to make: I could reinstall Minix, or I could bite the bullet and acknowledge that Linux was good enough that I didn’t need Minix. I would write the programs to compile Linux, under itself, and whenever I felt I needed Minix I would just add the desired feature to Linux. It’s a big conceptual step when you drop the original hosting environment and truly make a program self-hosting, so big that I released the new version as 0.10 in late November.

Of course, maybe he did do the same mistake twice :)

Reason0773• 3 years ago

In the early days of the iPhone you could jailbreak and get a tty into the baseband chip to do all kinds of cool stuff. And at least back in those days (iPhone 3GS/4/5 era), the Qualcomm baseband chips still very much used the AT command set. Took me right back to the BBS era.

I wonder if they still use AT commands today?

flangola7• 3 years ago

Are there any FOSS baseband systems?

anigbrowl• 3 years ago

More like a billion (soon to be trillion!). Hayes is still in use on pretty much all IOT modems. I was digging through the docs of some a few months ago and thinking 'welp, guess I have to learn about cellular data modems...sigh' only to find the chip maker's API involved sending AT commends to the hardware, and not much had changed in 30 years since I had lest needed them.

IOT hacking in general is a fun nostalgia trip. Edge device sims are limited to very paltry monthly data caps unless you want to pay fat money, and it's kinda fun to work within such tight constraints and think of ways to squeeze value out of every last byte.

rcarmo• 3 years ago

I used to know a bunch of those by heart from doing tech support at an ISP (and testing several different modems).

Fun fact: it’s all still there in a lot of mobile chipsets, just like fax emulation :)

Hayes command set history: The tech that dialed in a million modems

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