ENC28J60, how to get a dynamic destination IP addr.

I have been working with the ENC28J60 card working as UDP and kindly asking for help, how to get a dynamic destination IP addr. I want to send back data ex. temperature to this IP addr. who asking for it. At the moment I can only send data to a static IP destination.
I use the <EtherCard.h> and <IPAddress.h> and the code below works fine, except for, it use (ipDest) as static Destination IP.
The variable “src” contain the Destination IP. My problem is to parse “src” values into variable “ipDest”.

#include <EtherCard.h>
#include <IPAddress.h>

#define STATIC 1  // set to 1 to disable DHCP (adjust myip/gwip values below)

// ethernet interface ip address
static byte myip[] = { 192,168,1,6 };
// gateway ip address
static byte gwip[] = { 192,168,1,1 };
// DNS ip address
static byte dnsip[] = { 194,239,134,83 };

// ethernet mac address - must be unique on your network
static byte mymac[] = { 0x70,0x69,0x69,0x2D,0x30,0x31 };

byte Ethernet::buffer[500]; // tcp/ip send and receive buffer
int led = 5; 
char data;

String sDat;
byte ipDest[] = {192, 168, 1, 30};
unsigned int portDest = 9000;
unsigned int portMy = 1337;

// ***********************************************
void setup()
  Serial.println("\n[I'm listen..]");
  pinMode(led, OUTPUT);
  if (ether.begin(sizeof Ethernet::buffer, mymac) == 0)
    Serial.println( "Failed to access Ethernet controller");
  ether.staticSetup(myip, gwip, dnsip);
  if (!ether.dhcpSetup())
    Serial.println("DHCP failed");

  ether.printIp("IP:  ", ether.myip);
  ether.printIp("GW:  ", ether.gwip);
  ether.printIp("DNS: ", ether.dnsip);

  //register udpSerialPrint() to port 1337
  ether.udpServerListenOnPort(&udpSerialPrint, 1337);

  //register udpSerialPrint() to port 42.
 // ether.udpServerListenOnPort(&udpSerialPrint, 42);

// **********************************************
void loop()
  //this must be called for ethercard functions to work.

// ***********************************************
//callback that prints received packets to the serial port

void udpSerialPrint(word port, byte ip[4], const char *data, word len)
 IPAddress src(ip[0], ip[1], ip[2], ip[3]);
 Serial.println(src);   // Contain Destination IP
 Serial.println (data);
 char msg[] = {"TEMP = 21.4"};
 ether.sendUdp(msg, sizeof msg, portMy, ipDest, portDest);
// ***********************************************