View source for Arduino: Ethernet UDP Receive Data Switch LED

==Code==

 #include <SPI.h>        
 #include <Ethernet.h>
 #include <EthernetUdp.h>
 
 const int ledPin = 4; // the pin that the LED is attached to
 
 // Enter a MAC address and IP address for your controller below.
 // The IP address will be dependent on your local network:
 byte mac[] = {  
   0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
 IPAddress ip(192, 168, 0, 3);
 
 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() {
   // Open serial communications and wait for port to open:
   Serial.begin(9600);
   // initialize the LED pin as an output:
   pinMode(ledPin, OUTPUT);
   while (!Serial)
   {
     ; // wait for serial port to connect. Needed for native USB port only
   }
   // start the Ethernet and UDP:
   Ethernet.begin(mac,ip);
   Udp.begin(localPort);
 }
 
 void loop()
 {
   int packetSize = Udp.parsePacket();
   if(packetSize)
   {
     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);
     
     // if it's a capital H (ASCII 72), turn on the LED:
     if (packetBuffer[0] == 'H')
     {
       digitalWrite(ledPin, HIGH);
       Serial.println("LED ON\n");
     }
     // if it's an L (ASCII 76) turn off the LED:
     if (packetBuffer[0] == 'L') {
       digitalWrite(ledPin, LOW);
       Serial.println("LED OFF\n");
     }
   }
 }


==Client==

 nc -u 192.168.0.3 8888