modbus_receive - Man Page
receive an indication request
int modbus_receive(modbus_t *ctx, uint8_t *req);
The modbus_receive() function shall receive an indication request from the socket of the context ctx. This function is used by Modbus slave/server to receive and analyze indication request sent by the masters/clients.
If you need to use another socket or file descriptor than the one defined in the context ctx, see the function modbus_set_socket(3).
The function shall store the indication request in req and return the request 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.
The libmodbus documentation was written by Stéphane Raimbault <email@example.com>