---
name: "modbus_set_byte_timeout"
section: "3"
platform: "linux"
package: "libmodbus-dev"
version: "3.1.6-2.1"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/modbus_set_byte_timeout"
---

# modbus\_set\_byte\_timeout(3)

set timeout between bytes

## NAME

modbus\_set\_byte\_timeout - set timeout between bytes

## SYNOPSIS

**void modbus\_set\_byte\_timeout(modbus\_t \****ctx***, uint32\_t** *to\_sec***, uint32\_t** *to\_usec***);**

## DESCRIPTION

The **modbus\_set\_byte\_timeout()** function shall set the timeout interval between two consecutive bytes of the same message. The timeout is an upper bound on the amount of time elapsed before **select()** returns, if the time elapsed is longer than the defined timeout, an ETIMEDOUT error will be raised by the function waiting for a response.

The value of *to\_usec* argument must be in the range 0 to 999999.

If both *to\_sec* and *to\_usec* are zero, this timeout will not be used at all. In this case, **modbus\_set\_response\_timeout()** governs the entire handling of the response, the full confirmation response must be received before expiration of the response timeout. When a byte timeout is set, the response timeout is only used to wait for until the first byte of the response.

## RETURN VALUE

The function shall return 0 if successful. Otherwise it shall return -1 and set errno.

## ERRORS

**EINVAL**

The argument *ctx* is NULL or *to\_usec* is larger than 1000000.

## SEE ALSO

[**modbus\_get\_byte\_timeout**(3)](/modbus_get_byte_timeout/3.md) [**modbus\_get\_response\_timeout**(3)](/modbus_get_response_timeout/3.md) [**modbus\_set\_response\_timeout**(3)](/modbus_set_response_timeout/3.md)

## AUTHORS

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