Access to modbus_reply() response frame required

[anrodlo]

libmodbus version

3.1.11

OS and/or distribution

Linux (Debian Buster)

Environment

armel, armhf and amd64.

Description

The modbus response frame, constructed in modbus_reply() function, is not available via API.
Access to the real modbus traffic is needed for debugging, to diagnose communication problems.

Expected behavior or suggestion

I suggest to add an API function modbus_reply_construct() that constructs the response frame and retruns the content in a variable (rsp). Also send_msg() or a wrapper function (e.g. modbus_reply_send()) must be part of the API.

int modbus_reply_construct(modbus_t *ctx,
const uint8_t *req,
int req_length,
modbus_mapping_t *mb_mapping,
uint8_t *rsp)