If you prefer, you could also draw ASCII diagrams manually with asciiflow. I find this tool pretty handy from time to time.

http://asciiflow.com/

This looks useful. I really like the nwdiag python package. This has and packagediag which might be nice to get integrated with protocol.

http://blockdiag.com/en/nwdiag/index.html

Nice, I thought for a moment I could do SoC register diagrams with it as well but not so much: ./protocol "reserved:2,PLLSAI_RDY:1,PLLSAI_ON:1,PLI2S_RDY:1,PLL_RDY:1,PLL_ON:1,Reserved:4,CSS_ON:1,HSE_BYP:1,HSE_RDY:1,HSE_ON:1,HSICAL:8,HSITRIM:5,Reserved:1,HSI_RDY:1,HSI_ON:1"

0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |re.|P|P|P|P|P|Reserv.|C|H|H|H| HSICAL | HSITRIM |R|H|H| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

You should indent text by two (or more spaces) to make HN preserve whitespace: https://news.ycombinator.com/formatdoc

Let me fix it:

  $ protocol "reserved:2,PLLSAI_RDY:1,PLLSAI_ON:1,PLI2S_RDY:1,PLL_RDY:1,PLL_ON:1,Reserved:4,CSS_ON:1,HSE_BYP:1,HSE_RDY:1,HSE_ON:1,HSICAL:8,HSITRIM:5,Reserved:1,HSI_RDY:1,HSI_ON:1"
   0                   1                   2                   3  
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |re.|P|P|P|P|P|Reserv.|C|H|H|H|     HSICAL    | HSITRIM |R|H|H|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Cute output but terrible code. Unmaintained.

It would be a lot better if it could read from an established, broad, well maintained database like Wireshark (formerly ethereal).

Be careful when setting custom line widths, in the past i've run into situations where the last row of fields gets cutoff, depending on the line width.

Looks like a nice reference, in addition to supporting custom protocols.

It would be cool if it could also generate code to marshal and unmarshal a protocol.

As far as I can tell, it only deals with fixed width fields, and nothing of the detail inside them. No, notion, for example, of whether a field is big/little endian, protocols with delimited fields, variable length protocols with "length" followed by "field", etc.

Looks neat. Now this needs to become a plugin for ST3!

> ST3

I'll take it that's not Scream Tracker 3 (1994), Seattle's Sound Transit 3 ballot measure, or the New Jersey tax form, right?

Probably Sublime Text 3.

Makes sense, thanks!

This information belongs in manual pages on the system. On GNU/Linux operating systems, that's section 7; on illumos and SVR4 based systems, that'd be section 5.

What do you mean by "this information"?

The information which the program presents.

Honest question: Is there an audience for this besides network engineers?

For anything else, I'd prefer either a human-readable text-based protocol or something like Protobuf that generates (de)serializing code from a schema definition.

Absolutely. I've had to implement protocols from a spec using various guides that had really bad diagrams of how the data is laid out. This tool could have made them a lot better. And as others have pointed out its extremely useful for binary file type diagrams.

It makes a lot of sense for any kind of binary format as well (eg. gzip: https://tools.ietf.org/html/rfc1952).

Honest answer: yes.