NAME

       modbus_reply_exception - send an exception response

SYNOPSIS

       *int modbus_reply_exception(modbus_t *ctx, const uint8_t *req, unsigned int
       exception_code);

DESCRIPTION

       The modbus_reply_exception() function shall send an exception response based on the
       exception_code in argument.

       The libmodbus provides the following exception codes:

       •   MODBUS_EXCEPTION_ILLEGAL_FUNCTION (1)

       •   MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS (2)

       •   MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE (3)

       •   MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE (4)

       •   MODBUS_EXCEPTION_ACKNOWLEDGE (5)

       •   MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY (6)

       •   MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE (7)

       •   MODBUS_EXCEPTION_MEMORY_PARITY (8)

       •   MODBUS_EXCEPTION_NOT_DEFINED (9)

       •   MODBUS_EXCEPTION_GATEWAY_PATH (10)

       •   MODBUS_EXCEPTION_GATEWAY_TARGET (11)

       The initial request req is required to build a valid response.

RETURN VALUE

       The function shall return the length of the response sent if successful. Otherwise it
       shall return -1 and set errno.

ERRORS

       EINVAL
           The exception code is invalid

SEE ALSO

       modbus_reply(3) libmodbus(7)

AUTHORS

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