mbusd(8)

💅 mbusd 💅 — that's the page name, and yes it's section 8 of the System Manager's Manual, we love a system admin moment

okay so bestie, the page you're reading about is literally called mbusd, and near the top of the actual file it says mbusd(8) in the corner like a little name tag. now let's get into it 💖

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✨ SYNOPSIS ✨

here's the whole shape of it, copy-paste exact:

mbusd [-h] [-d] [-L logfile] [-v level] [-c cfgfile] [-p device] [-s
speed] [-m mode] [-t] [-r] [-y sysfsfile] [-Y sysfsfile] [-A address]
[-P port] [-C maxconn] [-N retries] [-R pause] [-W wait] [-T timeout]
[-b]

lowkey iconic bracket spam, but that's just how flags are born 🫶

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🦋 DESCRIPTION 🦋

mbusd is a MODBUS/TCP to MODBUS/RTU gateway. that's it, that's the sentence, and honestly she ate 🔥

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🎀 OPTIONS 🎀

this is the part where I hold your hand, bestie, because there are like a million of them and each one is a little gift:

• -h — usage help. the "help me please" flag ✨
• -d — tells mbusd not to fork itself (aka non-daemonize). she stays in the foreground with you, main character energy 👑
• -L logfile — picks the log file name. '-' means log to STDOUT only. the default is /var/log/mbusd.log 🍓
• -v level — sets how chatty the logging is. 0 = errors only, 1 = also warnings, 2 = also information messages. if mbusd was compiled in debug mode, valid log levels go all the way up to 9, and anything above 2 forces logging of information about additional internal events. so like, level 9 is her venting in her notes app 💀
• -c cfgfile — read configuration from cfgfile. yes queen, externalize your config 🙈
• -p device — sets the serial port device name 🔌
• -s speed — sets the serial port speed ⚡
• -m mode — sets the serial port mode (like 8N1). those three little characters are doing so much work ngl
• -S — enable RS-485 support for the given serial port device (Linux only 🐧, sorry not sorry to everyone else)
• -A address — sets the TCP address to bind 🌐
• -P port — sets the TCP port number 🚪
• -t — enable RTS RS-485 data direction control using RTS, active transmit 📤
• -r — enable RTS RS-485 data direction control using RTS, active receive 📥
• -y file — enable RS-485 direction data direction control by writing '1' to file for transmitter enable, and '0' to file for transmitter disable. ones and zeros, her love language 💜
• -Y file — same deal but flipped: writes '0' to file for transmitter enable, and '1' to file for transmitter disable. the evil twin, we stan 🌈
• -C maxconn — sets the maximum number of simultaneous TCP connections 👯‍♀️
• -N retries — sets the maximum number of request retries (0 = disable retries, no second chances fr fr)
• -R pause — sets the pause between requests, in milliseconds ⏸️
• -W wait — sets the response wait time, in milliseconds ⌛
• -T timeout — sets the connection timeout value, in seconds (0 = disable timeout, she waits forever, delulu but valid)
• -b — instructs mbusd to reply on a broadcast 📢 periodt

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💀 NOTES 💀

okay this is the drama section, pay attention:

• when mbusd gets a response with an invalid CRC and can't correct the error by re-requesting, it returns a MODBUS/TCP packet with exception code 04 💀
• when mbusd can't receive a response from the MODBUS RTU device at all (like, the addressed controller is just not present on the network, ghosted 👻), it returns a MODBUS/TCP packet with exception code 0x0B 😭

no cap, these codes are your best friends when things go sideways.

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🐛 BUGS 🐛

please send bug reports to the author. be nice about it, they're doing their best 🫶

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👑 AUTHORS 👑

the legends themselves:

• Victor Antonovich <v.antonovich@gmail.com>
• Andrew Denysenko <nitr0@seti.kr.ua>

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📜 LICENSE 📜

this program is distributed under the BSD license. see the LICENSE file in the installation directory for the full license text 📄✨

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and that's the whole page bestie!! you made it to the bottom, I'm obsessed 🎀 the version on this one is mbusd 0.5.3, dated 07 Apr 2026, and the page is mbusd(8) — mwah, go forth and gateway 💖🦋🌸