# modbus_reply(3) Manual Page

## NAME

modbus_reply - send a reponse to the received request

## SYNOPSIS

*int modbus_reply(modbus_t *ctx, const uint8_t *req, int req_length, modbus_mapping_t *mb_mapping);

## DESCRIPTION

The modbus_reply() function shall send a response to received request. The request req given in argument is analyzed, a response is then built and sent by using the information of the modbus context ctx.

If the request indicates to read or write a value the operation will done in the modbus mapping mb_mapping according to the type of the manipulated data.

If an error occurs, an exception response will be sent.

This function is designed for Modbus server.

## RETURN VALUE

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

## ERRORS

EMBMDATA

  Sending has failed

See also the errors returned by the syscall used to send the response (eg. send or write).

## SEE ALSO

modbus_reply_exception(3) libmodbus(7)

## AUTHORS

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