EthernetUDP.remoteIP()

// An EthernetUDP instance to let us send and receive packets over UDP
EthernetUDP Udp;

Udp.remoteIP();

#include <Ethernet.h>
#include <EthernetUdp.h>
 
// Enter an IP address for your controller below.
// The IP address will be dependent on your local network:
IPAddress ip(192, 168, 1, 177);
 
unsigned int localPort = 8888;      // local port to listen on
 
// An EthernetUDP instance to let us send and receive packets over UDP
EthernetUDP Udp;
 
void setup() {
  // start the Ethernet and UDP:
  Ethernet.begin(NULL,ip);
  Udp.begin(localPort);
}
 
void loop() {
  int packetSize = Udp.parsePacket();
 
  if(packetSize)
  {
    Serial.print("Received packet of size ");
    Serial.println(packetSize);
    Serial.print("From IP : ");
 
    IPAddress remote = Udp.remoteIP();
    //print out the remote connection's IP address
    Serial.print(remote);
 
    Serial.print(" on port : ");
    //print out the remote connection's port
    Serial.println(Udp.remotePort());
  }
}