MODBUS_SET_RESPONSE_(3)

📦
version 3.1.6 · 3 versions
, in debian bookworm

💖 MODBUS_SET_RESPONSE_(3) 💖

okay bestie, welcome to the libmodbus Manual — this is the page where we learn how long to sit around waiting for a reply before we're like "girl... hello??" 🕐✨

✨ NAME ✨

modbus_set_response_timeout — set timeout for response 🫶

✨ SYNOPSIS ✨

int modbus_set_response_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t
to_usec);

✨ DESCRIPTION ✨

So like, the modbus_set_response_timeout() function shall set the timeout interval used to wait for a response. That's it, that's the job 💅

Here's the tea tho — when a byte timeout is set, if the elapsed time for the first byte of response is longer than the given timeout, an ETIMEDOUT error will be raised by the function waiting for a response. 😭 She said times up.

And when byte timeout is disabled, the full confirmation response must be received before expiration of the response timeout. Like, the WHOLE thing, no partial credit, no half-sent texts. 📵

ngl there's a lil rule you cannot skip: the value of to_usec argument must be in the range 0 to 999999. Don't be out here wildin' with the microseconds. 🙈

✨ RETURN VALUE ✨

The function shall return 0 if successful. Otherwise it shall return -1 and set errno. bestie either ate or she didn't 💀

✨ ERRORS ✨

  • EINVAL — The argument ctx is NULL, or both to_sec and to_usec are zero, or to_usec is larger than 1000000.
lowkey three separate ways to trip, so vibe check your args before you call her 🌸

✨ EXAMPLE ✨

okay so here's the whole thing in action, no cap:

uint32_t old_response_to_sec;
uint32_t old_response_to_usec;

/* Save original timeout */
modbus_get_response_timeout(ctx, &old_response_to_sec, &old_response_to_usec);

/* Define a new timeout of 200ms */
modbus_set_response_timeout(ctx, 0, 200000);

see how she saves the old timeout first? that's main character energy right there — always know where you came from before you change the vibe 👑

✨ SEE ALSO ✨

go read those too, they're all in the same friend group fr fr 🦋

✨ AUTHORS ✨

The libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com> 💜

and that's the whole page, bestie!! this was libmodbus v3.1.6, dated 11/17/2025 — mwah, go set some timeouts responsibly, ily, byeeee 🎀✨🫶

📦 where this page comes from