modbus_receive_confirmation - receive a confirmation request
The modbus_receive_confirmation() function shall receive a request via the
socket of the context
ctx. This function must be used for debugging purposes
because the received response isn't checked against the initial request. This
function can be used to receive request not handled by the library.
The maximum size of the response depends on the used backend, in RTU the
array must be
MODBUS_RTU_MAX_ADU_LENGTH bytes and in TCP it must be
MODBUS_TCP_MAX_ADU_LENGTH bytes. If you want to write code compatible with
both, you can use the constant
MODBUS_MAX_ADU_LENGTH (maximum value of all
libmodbus backends). Take care to allocate enough memory to store responses to
avoid crashes of your server.
The function shall store the confirmation request in
rsp and return the
response length if successful. The returned request length can be zero if the
indication request is ignored (eg. a query for another slave in RTU
mode). Otherwise it shall return -1 and set errno.