Perhaps the oldest protocol for automated (in terms of encoding/decoding) text communication that's still being regularly used?

https://en.wikipedia.org/wiki/Baudot_code#ITA2

> In 1924, the CCITT introduced the International Telegraph Alphabet No. 2 (ITA2) code[14] as an international standard, which was based on the Western Union code with some minor changes.

> ITA2 is still used in telecommunications devices for the deaf (TDD), Telex, and some amateur radio applications, such as radioteletype ("RTTY").

It's interesting that the fundamentals of this were invented in 1870s. Who needs semiconductors when you have gears and levers?

https://en.wikipedia.org/wiki/Émile_Baudot

British naval signal and letter flags codified 1817.

Morse code from 1840s. Ham radio still uses it when signal took weak fir voice. Proficiency was required for a ham license until 2006.

In my college comp-sci networking class, one of our projects was to figure out a system for sending messages visually between two parties spaced 100 yards (91 meters) apart as quickly as possible.

Each team of four came up with their own signaling method, trying to balance how many bits were transmitted with each symbol with how quickly we could encode/decode the message.

Binoculars were not allowed. We were outside, so we didn't know how windy it would be.

I seem to recall on my team, we were sending two bits per symbol. I think it was just a large cardboard box, we colored each of the four flaps visually distinct, then unfolded one of the flaps for each symbol.

I don't recall a single team thinking to re-purpose naval flags.

Duh.

https://en.wikipedia.org/wiki/Flag_semaphore would have been good if you needed to send arbitrary text.

Naval flags would be higher bandwidth if you could pre-arrange a modest-sized dictionary of the words and phrases you’d need.

https://www.navalgazing.net/Signalling-Part-1 is a good read.

It’s been over two decades but I think the requirement may have been an arbitrary bitstream but if not that, it was likely any of the visible ASCII characters.

There is also flag semaphore which is very fast and very recognizable and gives you about 5 bits per signal.

Morse may not be the oldest but my bet is on it being by far the most widely still used of anything nearly two centuries old. I got into ham radio a decade ago and learned Morse (poorly) just because. It already wasn't a requirement, but so many still use it.

Hopefully there's an app for listening to it and interpreting it? I bet those old timers get pretty fast with the Morse

Braille is originally from a similar timeframe and carries six bits. Modern enhancements have focused on the protocol above the payload to make it more efficient.

If that counts, then so do Chinese characters (1200 BC or older)

Interesting question and I guess it depends what you mean by "protocol"[1]. If simple characters-over-the-wire counts, then ASCII was developed throughout 60s and was itself derived from much older telegraph standards. Teletype is arguably more of a "protocol" and is actually even older, going back to the 50s, and arguably the 30s in some form, and still forms the basis of all terminal computing today including (especially) across networks.

[1] Sometimes it seems like every interesting discussion boils down to definitions, doesn't it?

If we're limiting it to "used by computers", and "actually used in some meaningful non-hobby volume" maybe the T1/DS1 TDMA protocol? That dates back to 1962.

Or maybe morse code counts as a protocol?, Still around in VOR (VHF omnidirectional range) and NDB (Non-directional beacon) in the aviation world.

RS-232 (1960) is still going strong.

Snail-mail ain't dead yet.

I believe Semaphore predates it

How so? Mail couriers are surely much older than semaphore systems of any kind.

IBM z/OS (né OS/360) is 57 years old and still actively developed, so maybe something used there?

"What's the oldest protocol that's still regularly used?"

People are answering with old telephone codes and British naval signals, etc.

You should be thinking:

- The muslim call to prayers.

- The affirmation of faith, as it is spoken in mass or (protestant) church ... or the first and second readings, followed by a Gospel reading.

- The Jewish rite of circumcision (which is, among other things, almost certainly a signaling mechanism).

If we're abandoning automation:

https://en.wikipedia.org/wiki/Protocol_(diplomacy)

> The term protocol is derived, via French and Medieval Latin, from the Greek word πρωτόκολλον protokollon "first glued sheet of or onto a papyrus-roll".

> The rules of protocol to create space where meetings can take place.

https://www.protocol.dubai.ae/About/Protocol-History

> The diplomatic relations that existed between Egypt and Babel, which started in 1450 B.C., included highlights on the application of standards for Protocol and Etiquette that were related to both diplomatic immunities as well as receptions and ceremonies.

I would hate to be involved with any generic means of communication that required circumcisions to impart information. That sounds like a rather gory way to tell my wife I'll be late for dinner.

But it was a great way to tell your wife not to make pork for dinner. At least until it caught on beyond the intended market.

That depends on how you define "protocol". ASCII dates from 1963, and that's still the baseline for text-based protocols.

FTP predates Ethernet, Token Ring and ARCNET. It predates TCP/IP. For an actual protocol, and not just a simple format specification like ASCII, it doesn't get older than that in current use.

ASCII is a very obvious format. If you take the english alphabet and symbols, it fits almost perfectly in the first 7 bits. In 5th grade I tried encoding English in binary, and noticed how I accidentally reinvented ASCII.

I wouldn't say it's obvious. There's some careful decisions in the design that might not be obvious at first sight, such as having upper and lowercase characters be the same save for a single bit.

Or the numbers 0 to 9 at 48 to 57 (ie just mask out bits 4 and 5)

I see. I would retract my statement if HN let me edit.

Retract it at the bottom where it is least likely to be seen like we do in modern papers/news sites.

Encode English in Binary in 5th grade? You must be a smart cookie.

In 5th grade, I had the attention span of a fruit fly. Probably would have tried drawing phalluses in ascii if I had known about it.

Morse would be older.

Ha, I was like "REALLY!?!?" before actually clicking the link. I was thinking of: https://en.wikipedia.org/wiki/Shibboleth_Single_Sign-on_arch...

...which is an unlikely contender for oldest protocol!

You can consider it a successor protocol :-)

DTMF “touch tone” telephone dialling dates from 1963

100V DC T1 lines still exist, I'm told

XON/XOFF?