MODBUS_RECEIVE(3)

💖 MODBUS_RECEIVE(3) 💖

okay bestie, welcome to the libmodbus manual — yes it's a real manual, yes it's for the C library, and yes we're gonna make it cute. this one's all about modbus_receive, and it's genuinely one of the most iconic functions in here. let's get into it 🫶

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✨ NAME ✨

modbus_receive — receive an indication request

🌸 SYNOPSIS 🌸

int modbus_receive(modbus_t *ctx, uint8_t *req);

💅 DESCRIPTION 💅

so the modbus_receive() function shall receive an indication request from the socket of the context ctx. that's the whole vibe. ✨

this function is the one the Modbus slave/server uses to receive and analyze indication requests that the masters/clients send over. like, the server is just sitting there being gorgeous and this is how it hears what the clients are asking for. no cap. 👑

if you need to use a different socket or file descriptor than the one defined in the context ctx, go look at modbus_set_socket(3) — that's the one that lets you swap the socket out. 💫

🎀 RETURN VALUE 🎀

on success, the function shall store the indication request in req and return the request length. slay. 🍓

but here's the lil plot twist: the returned request length can be zero if the indication request is ignored — for example, a query for another slave in RTU mode. it's giving "not my business, not my problem." 🙈

otherwise it shall return -1 and set errno. so if you see that -1, check your errno, bestie. 😭

fr fr, don't ignore that errno. it's literally the only clue you get.

🔥 SEE ALSO 🔥

• modbus_set_socket(3)
• modbus_reply(3)

👑 AUTHORS 👑

the libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com> — absolute legend, main character energy, we stan. 💜

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and that's the whole page, bestie! this was libmodbus v3.1.6, dated 11/17/2025 — periodt. 💅✨ 🦋