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Bye CUPS: Printing with Netcat

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Re: Bye CUPS: Printing with Netcat

#71

Post by anthk »

gerdesj wrote: post #54
krrrh wrote: post #36

Earlier quoted context omitted.

When I was first learning Linux many years ago a friend and I got intoxicated and catted /dev/hda into /dev/dsp. It was all basically static with sometimes very structured patterns that we would try to guess as to what filetype was producing them. He had download and forgotten about a long uncompressed audio recording of a piano performance on his drive that suddenly started breaking through the static in chunks of v…

Good skills. It has never occurred to me to do that but it is actually quite an obvious thing to do when you "know" that everything is a file. Any idea what the visual equivalent would be?

Plan9's /dev/draw.

Re: Bye CUPS: Printing with Netcat

#73

Post by ajnin »

chrisseaton wrote: post #64
jim-jim-jim wrote: post #8

Hah. I had a similar moment of enlightenment with FreeBSD when somebody explained that you can just cat a wav file into /dev/audio (or /dev/dsp? forget the exact name). And that you can produce white noise by catting /dev/random to the same destination. With no barrier to the sound card like that, I was free to experiment with programming dfferent noise algorithms and figuring out how digital audio works. I eventuall…

How do the device files know what format the audio data is in?

It doesn't, it just plays the data as PCM and with whatever sample format and sample rate it is currently configured for.

Re: Bye CUPS: Printing with Netcat

#74

Post by askvictor »

corbet wrote: post #21

FWIW, the Internet Printing Protocol (and IPP Everywhere in particular) make printer setup in CUPS far, far easier, but distributors seem reluctant to encourage it. I wrote about my experiences with IPP back in June ( https://lwn.net/Articles/857502/ ). I expect to never have to hassle with printer drivers again...

I thought that the whole point of CUPS was to provide an IPP service.

Re: Bye CUPS: Printing with Netcat

#75

Post by mbreese »

mackman wrote: post #3

My first introduction to the internet was downloading Magic the Gathering card lists as postscript files via FTP and then FTPing them to a postscript printer. Would have been 1994 and they were some sort of Sun machine at LMU. Internet has been all downhill since then.

A few years later (2002-ish), I setup a Zebra barcode/label printer that had a similar mechanism. I’d write the code for the label in the printers language (ZPL?) and then FTP a file to the printer.

I was in grad school in a wetlab, so I had to label a ton of microcentrifuge tubes. Having a quick web interface e to generate the ZPL files that would be FTP’d to the printer let me avoid writing all of that out by hand.

It was such a simple system. And the FTP server was basically a queue, so you could print a bunch of labels at a time.

Re: Bye CUPS: Printing with Netcat

#76

Post by feanaro »

rescbr wrote: post #56
int_19h wrote: post #55

Earlier quoted context omitted.

I remember back when ALSA was a hot new thing on Linux, and it kinda sorta solved the "only one app can play things at the same time" problem that existed with the traditional OSS. Meanwhile, OSS on FreeBSD just worked.

Rinse & repeat when every desktop environment brought their own audio daemons, then later PulseAudio and now PipeWire. I still roll my eyes and I don’t get surprised every couple of years when somebody releases a yet another Linux audio daemon. Maybe it’s some kind of Linux tradition. At least PipeWire is saner compared to PulseAudio.

> At least PipeWire is saner compared to PulseAudio.

In what way?

Re: Bye CUPS: Printing with Netcat

#77

Post by ta988 »

rescbr wrote: post #56
int_19h wrote: post #55

Earlier quoted context omitted.

I remember back when ALSA was a hot new thing on Linux, and it kinda sorta solved the "only one app can play things at the same time" problem that existed with the traditional OSS. Meanwhile, OSS on FreeBSD just worked.

Rinse & repeat when every desktop environment brought their own audio daemons, then later PulseAudio and now PipeWire. I still roll my eyes and I don’t get surprised every couple of years when somebody releases a yet another Linux audio daemon. Maybe it’s some kind of Linux tradition. At least PipeWire is saner compared to PulseAudio.

Since I switched to pipewire, my audio is crackling every time the cpu is loaded (a ryzen 7...) not even jack was struggling with that on this machine

Re: Bye CUPS: Printing with Netcat

#78

Post by neilv »

Two downsides to being able to send PDF bytes direct to TCP port 9100 hosted directly by the printer firmware on the printer's own network interface...

* That's not encrypted.

* (More importantly) You might look at the printer firmware's complexity, excessive IoT/cloud-friendliness, and hints from the printer brand about their current engineering standards... and become uneasy about plugging that into your LAN, even if you firewall it to heck.

Partial solution: for my modern laser printer, I've left its NIC unconnected, and put my own print server in front of it, on a VLAN, and connected via USB. And I still strongly suspect at least a couple classes of vulnerability still present, but no time to look into it or mitigate.

Variation for the article's needs: you can make a one-line script TLS/SSL tunnel from a local port on your workstation host(s), to a thin isolating host (old RasPi?) in front of the printer. So content is encrypted over the LAN, and the printer is more isolated than it would be normally.

Another variation: plug the printer directly into a single host that needs it (such as via USB or a dedicated Ethernet NIC), and then decide what to do about any other hosts that want to use the printer.

Re: Bye CUPS: Printing with Netcat

#79

Post by qiqitori »

krrrh wrote: post #36
jim-jim-jim wrote: post #8

Hah. I had a similar moment of enlightenment with FreeBSD when somebody explained that you can just cat a wav file into /dev/audio (or /dev/dsp? forget the exact name). And that you can produce white noise by catting /dev/random to the same destination. With no barrier to the sound card like that, I was free to experiment with programming dfferent noise algorithms and figuring out how digital audio works. I eventuall…

When I was first learning Linux many years ago a friend and I got intoxicated and catted /dev/hda into /dev/dsp. It was all basically static with sometimes very structured patterns that we would try to guess as to what filetype was producing them. He had download and forgotten about a long uncompressed audio recording of a piano performance on his drive that suddenly started breaking through the static in chunks of v…

for i in $(seq 1 10); do seq -120 1 120; seq 120 1 -120; done | aplay

It's for you.

Re: Bye CUPS: Printing with Netcat

#80

Post by coryrc »

int_19h wrote: post #55
jim-jim-jim wrote: post #8

Hah. I had a similar moment of enlightenment with FreeBSD when somebody explained that you can just cat a wav file into /dev/audio (or /dev/dsp? forget the exact name). And that you can produce white noise by catting /dev/random to the same destination. With no barrier to the sound card like that, I was free to experiment with programming dfferent noise algorithms and figuring out how digital audio works. I eventuall…

I remember back when ALSA was a hot new thing on Linux, and it kinda sorta solved the "only one app can play things at the same time" problem that existed with the traditional OSS. Meanwhile, OSS on FreeBSD just worked.

OSS got that ability decades ago, yet we still have ALSA and then the others :(
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