arduino modbus function code 16

arduino_modbus.ino

#include <SPI.h>
#include <Ethernet.h>

byte mac[] = { 0x4E, 0xFB, 0xDD, 0x13, 0x06, 0x28 };
IPAddress ip(10, 0, 0, 50);
byte server[] = { 10, 0, 0, 17 };
EthernetClient client;

void setup()
{
  Ethernet.begin(mac, ip);
  Serial.begin(9600);
  client.connect(server, 502);
}

int i = 0;

void loop()
{
  // Write tanks
  byte writeModbus[17] = {0x00, 0x01, 0x00, 0x00, 0x00, 0x0b, 0x01, 0x10, 0x13, 0x8a, 0x00, 0x02, 0x04, 0x00, i++ % 100, 0x00, 0x38};
  client.write(writeModbus, 17);
  
  delay(1000);
}