Arduino/libraries/Ethernet/examples/UDPSendReceiveString/UDPSendReceiveString.pde

/*
  UDPSendReceive.pde:
 This sketch receives UDP message strings, prints them to the serial port
 and sends an "acknowledge" string back to the sender
 
 A Processing sketch is included at the end of file that can be used to send 
 and received messages for testing with a computer.
 
 created 21 Aug 2010
 by Michael Margolis
 
 This code is in the public domain.
 */


#include <SPI.h>         // needed for Arduino versions later than 0018
#include <Ethernet.h>
#include <Udp.h>         // UDP library from: bjoern@cs.stanford.edu 12/30/2008


// 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 };
byte ip[] = { 
  192,168,1,177 };

unsigned int localPort = 8888;      // local port to listen on

// the next two variables are set when a packet is received
byte remoteIp[4];        // holds received packet's originating IP
unsigned int remotePort; // holds received packet's originating port

// buffers for receiving and sending data
char packetBuffer[UDP_TX_PACKET_MAX_SIZE]; //buffer to hold incoming packet,
char  ReplyBuffer[] = "acknowledged";       // a string to send back

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

void setup() {
  // start the Ethernet and UDP:
  Ethernet.begin(mac,ip);
  Udp.begin(localPort);

  Serial.begin(9600);
}

void loop() {
  // if there's data available, read a packet
  int packetSize = Udp.available(); // note that this includes the UDP header
  if(packetSize)
  {
    packetSize = packetSize - 8;      // subtract the 8 byte header
    Serial.print("Received packet of size ");
    Serial.println(packetSize);

    // read the packet into packetBufffer and get the senders IP addr and port number
    Udp.readPacket(packetBuffer,UDP_TX_PACKET_MAX_SIZE, remoteIp, remotePort);
    Serial.println("Contents:");
    Serial.println(packetBuffer);

    Udp.sendPacket( ReplyBuffer, remoteIp, remotePort);
  }
  delay(10);
}


/*
  Processing sketch to run with this example
 =====================================================
 
 // Processing UDP example to send and receive string data from Arduino 
 // press any key to send the "Hello Arduino" message
 
 
 import hypermedia.net.*;
 
 UDP udp;  // define the UDP object
 
 
 void setup() {
 udp = new UDP( this, 6000 );  // create a new datagram connection on port 6000
 //udp.log( true ); 		// <-- printout the connection activity
 udp.listen( true );           // and wait for incoming message  
 }
 
 void draw()
 {
 }
 
 void keyPressed() {
 String ip       = "192.168.1.177";	// the remote IP address
 int port        = 8888;		// the destination port
 
 udp.send("Hello World", ip, port );   // the message to send
 
 }
 
 void receive( byte[] data ) { 			// <-- default handler
 //void receive( byte[] data, String ip, int port ) {	// <-- extended handler
 
 for(int i=0; i < data.length; i++) 
 print(char(data[i]));  
 println();   
 }
 */