EthernetUDP.available()

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

Udp.available()

#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;
 
char packetBuffer[UDP_TX_PACKET_MAX_SIZE]; //buffer to hold incoming packet,
 
void setup() {
  // start the Ethernet and UDP:
  Ethernet.begin(NULL,ip);
  Udp.begin(localPort);
}
 
void loop() {
  int packetSize = Udp.parsePacket();
 
  if(Udp.available())
  {
    Serial.print("Received packet of size ");
    Serial.println(packetSize);
    Serial.print("From ");
    IPAddress remote = Udp.remoteIP();
    for (int i =0; i < 4; i++)
    {
      Serial.print(remote[i], DEC);
      if (i < 3)
      {
        Serial.print(".");
      }
    }
    Serial.print(", port ");
    Serial.println(Udp.remotePort());
 
    // read the packet into packetBufffer
    Udp.read(packetBuffer,UDP_TX_PACKET_MAX_SIZE);
    Serial.println("Contents:");
    Serial.println(packetBuffer);
 }
}