ArduinoModbus : Modbus Client class
Begin the process of a writing multiple coils or holding registers.
Use write(value) to set the values you want to send, and endTransmission() to send request on the wire.
int beginTransmission(int type, int address, int nb);
int beginTransmission(int id, int type, int address, int nb);
id (slave) - id of target, defaults to 0x00 if not specified
type - type of write to perform, either COILS or HOLD_REGISTERS
address - start address to use for operation
nb - number of values to write
1 on success, 0 on failure
ModbusClient Class