LISTEN(1)

💖 LISTEN(1) — the listen page, bestie edition 💖

okay so this is listen from the Linux Programmer's Manual, and she is literally the girl who watches everything on your AX.25 network. no cap. let's get into it 🦋

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✨ NAME ✨

listen — monitor AX.25 traffic 👀📡

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🌸 SYNOPSIS 🌸

listen [-8] [-a] [-c] [-h] [-i] [-p port] [-r] [-t..] [-v]

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🎀 DESCRIPTION 🎀

So listen uses SOCK_PACKET facilities to give you a whole network monitor of all the AX.25 traffic your system hears. and the best part? since KISS is implicitly promiscuous, you don't need to do any special driver configurations. none. zero. she just works 💅

This version displays standard AX.25, PE1CHL extended AX.25, NET/ROM, Rose, ARP, IP, ICMP, TCP and UDP. She also displays IP, TCP, ICMP, TCP and UDP encapsulated within NET/ROM frames. (yes we said TCP twice, that's the original, don't come for me 🙈) The program also displays AX.25 and IP encapsulated within an IP frame — but see RFC1326 for reasons not to do so, bestie, that's a whole situation.

listen also makes an attempt at decoding some of the more common routing protocols. RSPF and RIP (both "normal" and G8BPQs RIP98) are traced. JNOS style NET/ROM node polls are also displayed. she's thorough like that ✨

And she can use colors to make the output more readable — the ncurses library is what accomplishes this. Color support defaults to being disabled, and the -c parameter is what enables it. slay.

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✨ OPTIONS ✨

• -8 — says your terminal is capable of printing 8-bit characters. this parameter is required for the -i parameter to work, so they're a package deal 🫶
• -a — lets you monitor outgoing frames too, not just incoming ones. both directions, we love a girl who sees everything 👑
• -c — enable color support 🌈
• -h — dumps the data portion of the packet in both hexadecimal and ASCII. the default is to display data as ASCII only.
• -i — maps IBM codepage 437 characters 128-158 to their ISO-Latin-1 equivalents. this is a hack for scandinavian users 🇸🇪 and it's only valid when used with the -8 and -c parameters.
• -p port — monitor only those frames received on a particular port. by default all AX.25 devices are monitored.
• -r — dumps the data portion in a "readable" fashion, which is more suitable for tracing plaintext AX.25 traffic. CR-LF conversion is done. cute and functional 💖
• -t — don't print a timestamp on each dump line.
• -tt — print an unformatted timestamp on each dump line.
• -ttt — print a delta (micro-second resolution) between current and previous line on each dump line. ⏱️
• -tttt — print a timestamp in default format proceeded by date on each dump line.
• -ttttt — print a delta (micro-second resolution) between current and first line on each dump line. the long haul delta, iconic.
• -v — display the version. that's it, that's the whole job 💅

the more ts you stack, the more timestamp she gives you. that's the vibe check, iykyk.

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🦋 FILES 🦋

• /etc/ax25/axports

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🌟 SEE ALSO 🌟

call(1), mheard(1), beacon(1), ax25(4), netrom(4), rose(4), kissattach(8).

go read those next, bestie, the lore goes deep 📚

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💀 BUGS 💀

ngl, listen does not validate the checksums of frames that support them (ie IP), therefore corrupt frames will be displayed with bogus values. so like… take those numbers with a grain of salt 🧂

Also: the MSS of a TCP frame that contains that option is not displayed. just not shown. we don't know why. it's giving mystery 🙈

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💜 AUTHORS 💜

• Alan Cox GW4PTS <alan@cymru.net>
• Jonathan Naylor G4KLX <g4klx@g4klx.demon.co.uk>
• Phil Karn KA9Q <karn@qualcomm.com>
• Heikki Hannikainen OH7LZB <oh7lzb@sral.fi>
• Scott Miller N1VG <scott@opentrac.org>

absolute legends, every single one 🌟 the way they built all this… obsessed.

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and that's the whole page, bestie!! 🎀 this was Linux, dated 27 August 1996 — yeah she's vintage but she still eats 💅 periodt. now go monitor some packets, main character. 💖✨