ArduinoUPDCommunicationWithCSharp.ino

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



// network configuration. dns server, gateway and subnet are optional.

 // the media access control (ethernet hardware) address for the shield:
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };  

// the dns server ip
IPAddress dnServer(192, 168, 1, 1);
// the router's gateway address:
IPAddress gateway(192, 168, 1, 1);
// the subnet:
IPAddress subnet(255, 255, 255, 0);

//the IP address is dependent on your network
IPAddress ip(192, 168, 1, 27);

// udp config

unsigned int localPort = 808;       // local port to listen for UDP packets

char packetBuffer[UDP_TX_PACKET_MAX_SIZE];
char ReplyBuffer[]="OK";

EthernetUDP Udp;



void setup() {
pinMode(4, OUTPUT);
  digitalWrite(4, LOW);
  
  Serial.begin(9600);

  // initialize the ethernet device
  Serial.print("Connecting to Router");
  //Ethernet.begin(mac);
  Ethernet.begin(mac, ip, dnServer, gateway, subnet);
  //Ethernet.begin(mac, ip, dnServer);
  //print out the IP address
  Serial.print("IP = ");
  Serial.println(Ethernet.localIP());

//udp begin
   Udp.begin(localPort);
}

void loop() {
//if theres data available, read a packet
int packetSize = Udp.parsePacket();

if(packetSize)
  {
    //read the packet into packetBuffer
    Udp.read(packetBuffer,UDP_TX_PACKET_MAX_SIZE);


    Serial.print("Received packet of size ");
    Serial.println(packetSize);
    
//read packets datata...
 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); //Dsiplay receive data to SerialPort
    
//read packet data.. end







    //send a reply to the IP address and porst that send us the packet we received

    Udp.beginPacket(Udp.remoteIP(),Udp.remotePort());
    Udp.println(ReplyBuffer);
    Udp.endPacket();
    
    }

    delay(10);
}