Not able to decode ModbusTCPServer.Poll(); function to get the Function code for read or write Operation.

[prakashvenugopal2014]

Not able to decode ModbusTCPServer.Poll(); function to get the Function code for Whether the Function code is for read or write Operation. Need functions to get the PDU that is Function code, Address & Data seperately and need response function to send the response to the Client Master
Here is the code Example:

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

bool _1s;
unsigned long TimeAct, TimePrev, HoldingResult, InputResult, HeartBeat, i, StartingAddr;
long Cmd;

EthernetServer EthServer(502);
ModbusTCPServer modbusTCPServer;

void setup() {
  // Ethernet Settings
  byte mac[] = { 0x4E, 0xA0, 0xBE, 0x3F, 0xFE, 0x0F };  // Define MAc address
  byte ip[] = { 192, 168, 1, 23 };                      // Define IP address
  byte subnet[] = { 255, 255, 255, 0 };                 // Define SubNEt mask

  // initialize the ethernet device
  Ethernet.begin(mac, ip, subnet);  // Assign MAC, IP, and subnet mask
  Serial.begin(9600);
  EthServer.begin();        // start listening for clients
  modbusTCPServer.begin();  // start listening for clients

  // Define Holding register:
  HoldingResult = modbusTCPServer.configureHoldingRegisters(0, 100);
  InputResult = modbusTCPServer.configureInputRegisters(0, 100);

  Serial.print("Holding Reg init result =");
  Serial.print(HoldingResult);
  Serial.print("\n");

  Serial.print("Input Reg init result =");
  Serial.print(InputResult);
  Serial.print("\n");

  Serial.print("Modbus server address=");
  Serial.println(Ethernet.localIP());
  Serial.print("\n");
}

void loop() {
  // Modbus server accept incoming connections
  EthernetClient client = EthServer.available();

  if (client.connected()) {
    modbusTCPServer.accept(client);
    // poll for Modbus TCP requests, while client connected
    modbusTCPServer.poll();
    // Serial.print("poll");
  }
  // Code Stuff needed to get the Function Code, Address, &Data
  //---------------------------------------------------------------------------------
  // Modbus server :

  // holding resgiter 40001: heartbeat (FC3)
  modbusTCPServer.holdingRegisterWrite(0x00, HeartBeat);

  // holding resgiter 40500: Command Word (FC6)
  Cmd = modbusTCPServer.holdingRegisterRead(90);
}