Tech insights

Internet Printing Protocol Printing with  Internet Printing Protocol (IPP)  involves sending a Unirast   Format (URF) image with appropriate protocol headers to port 631. It is the basis for standards like  Windows Mopria Alliance , Apple   AirPrint , and IPP Everywhere .  It is also called  Driverless Printing   since this doesn't involve installing any printer specific driver. On Plan 9, printing involves three steps: Convert the document to PDF using lp Convert the PDF to URF using  gs  (use urfgray, urfrgb or urfcmyk device) Send the request to the printer using hget IPP header ( req.bin in the below script) contains page output options like paper size, margins etc. This is generated   using ippenc.c .        #!/bin/rc HOST=$1 FILE=$2 TFILE=/tmp/a.pdf URL=( http://$HOST:631/ipp/print/ ) if (! ~ $#* 2)    echo 'Usage: $0 <printer-ip> <file>'     lp -d stdout $FILE > $TFILE...

Video pipeline in action Two important points about videos: A video is a series of images. RGB format is used for display. YUV format is used for storage and transmission.  Recording   ──────────────────────────────────────────────────────── [Video Source] → [Frame Processing] → [Video Encode] ┐                                                                                                      ├→ [Mux] → [Container Stream] [Audio Source] → [Audio Processing] → [Audio Encode] ┘ Playback   ──────────────────────────────────────────────────────── [Container Stream] → [Demux] → [Video Decode] → [Video Sink]                                   ...

Stream a single window or the whole screen via Real Time Streaming Protocol (RTSP). This uses MJPEG stream over TCP-interleave . Plan 9 /dev/screen and /dev/window produces RGBA byte stream with Plan 9 headers. This is converted to JPEG using tojpg and streamed using RTSP. In the video, host port 12554 port is being forwarded to 554 in the Plan 9 VM.  ffplay -rtsp_transport tcp rtsp://localhost:12554/ stream1       Code https://gitlab.com/atamariya/plan9front/-/blob/dev/sys/src/cmd/rtsp/server.c https://gitlab.com/atamariya/plan9front/-/blob/dev/sys/src/cmd/jpg/tojpg.c https://gitlab.com/atamariya/plan9front/-/blob/dev/sys/src/cmd/jpg/writejpg.c ( Update 16/03/2026 : server.c is moved to /sys/src/cmd/stream/rtsp/)   Youtube Live Use Real-Time Messaging Protocol ( RTMP ) to feed into Youtube / Twitch Live. video/hj264 -f 25 /dev/screen | video/rtmp -a /dev/audio rtmp://.... rtmp://...         Note:   The encoder and the publisher pr...

  Demo of Wifi router connection using WiFi Protected Setup (WPS). WiFi Protected Setup (WPS) allows you to connect to an Access Point (router) via Push Button Control (PBC) or a temporary PIN.   Authentication Flow   Direction Message / Contents Phase / Purpose Supplicant → AP Authentication Request 802.11 Authentication Supplicant ← AP Authentication Response Supplicant → AP Association Request 802.11 Association Supplicant ← AP Association Response Supplicant → AP EAPOL-Start EAP Initiation Supplicant ← AP EAP-Request Identity Supplicant → AP EAP-Response Identity (Identity: “WFA-SimpleConfig-Registrar-1-0”) Supplicant ← AP WSC Start Enrollee → Registrar (M1) N1 || Descripti...