MODBUS_REPLY(3)

💖 MODBUS_REPLY(3) 💖

ok so bestie, we're in the libmodbus Manual today and this page is literally about one function: modbus_reply. buckle up 🎀

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✨ NAME ✨

modbus_reply — send a response to the received request 🫶

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🌸 SYNOPSIS 🌸

int modbus_reply(modbus_t *ctx, const uint8_t *req, int req_length,
modbus_mapping_t *mb_mapping);

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🦋 DESCRIPTION 🦋

okay so the modbus_reply() function shall send a response to a received request. the request req that you hand it as an argument gets analyzed, then a response gets built and sent using all the info from the modbus context ctx. it's giving very thorough 💅

if the request says to read or write a value, the operation will be done in the modbus mapping mb_mapping, depending on the type of the manipulated data. like, whatever kind of data it is, that's where it lands ✨

if an error happens, an exception response will be sent. no cap.

💡 this function is designed for Modbus server. server girlies, this one's for you 👑

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⭐ RETURN VALUE ⭐

the function shall return the length of the response sent if everything went well, iykyk. otherwise it shall return -1 and set errno. sad but honest 😭

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💀 ERRORS 💀

• EMBMDATA — sending has failed. it's giving L, ngl 🙈

also see the errors returned by the syscall used to send the response (eg. send or write). those ones show up too, so check them fr fr.

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👑 SEE ALSO 👑

• modbus_reply_exception(3)
• libmodbus(7)

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💜 AUTHORS 💜

the libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com> — thank you icon, we owe you everything 🫶🌸

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and that's the whole page bestie!! this was libmodbus v3.1.6, dated 11/17/2025. go slay some Modbus servers, mwah 💅✨💖