Send and Receive UDP String

/*

  WiFi UDP Send and Receive String

 This sketch wait an UDP packet on localPort using a WiFi shield.

 When a packet is received an Acknowledge packet is sent to the client on port remotePort

 Circuit:

 * WiFi shield attached

 created 30 December 2012

 by dlf (Metodo2 srl)

 */

#include <SPI.h>
#include <WiFi.h>
#include <WiFiUdp.h>

int status = WL_IDLE_STATUS;
char ssid[] = "yourNetwork"; //  your network SSID (name)
char pass[] = "secretPassword";    // your network password (use for WPA, or use as key for WEP)
int keyIndex = 0;            // your network key Index number (needed only for WEP)

unsigned int localPort = 2390;      // local port to listen on

char packetBuffer[255]; //buffer to hold incoming packet
char  ReplyBuffer[] = "acknowledged";       // a string to send back

WiFiUDP Udp;

void setup() {

  //Initialize serial and wait for port to open:

  Serial.begin(9600);

  while (!Serial) {

    ; // wait for serial port to connect. Needed for native USB port only

  }

  // check for the presence of the shield:

  if (WiFi.status() == WL_NO_SHIELD) {

    Serial.println("WiFi shield not present");

    // don't continue:

    while (true);

  }

  String fv = WiFi.firmwareVersion();

  if (fv != "1.1.0") {

    Serial.println("Please upgrade the firmware");

  }

  // attempt to connect to Wifi network:

  while (status != WL_CONNECTED) {

    Serial.print("Attempting to connect to SSID: ");

    Serial.println(ssid);

    // Connect to WPA/WPA2 network. Change this line if using open or WEP network:

    status = WiFi.begin(ssid);

    // wait 10 seconds for connection:

    delay(10000);

  }

  Serial.println("Connected to wifi");

  printWifiStatus();

  Serial.println("\nStarting connection to server...");

  // if you get a connection, report back via serial:

  Udp.begin(localPort);
}

void loop() {

  // if there's data available, read a packet

  int packetSize = Udp.parsePacket();

  if (packetSize) {

    Serial.print("Received packet of size ");

    Serial.println(packetSize);

    Serial.print("From ");

    IPAddress remoteIp = Udp.remoteIP();

    Serial.print(remoteIp);

    Serial.print(", port ");

    Serial.println(Udp.remotePort());

    // read the packet into packetBufffer

    int len = Udp.read(packetBuffer, 255);

    if (len > 0) {

      packetBuffer[len] = 0;

    }

    Serial.println("Contents:");

    Serial.println(packetBuffer);

    // send a reply, to the IP address and port that sent us the packet we received

    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());

    Udp.write(ReplyBuffer);

    Udp.endPacket();

  }
}

void printWifiStatus() {

  // print the SSID of the network you're attached to:

  Serial.print("SSID: ");

  Serial.println(WiFi.SSID());

  // print your WiFi shield's IP address:

  IPAddress ip = WiFi.localIP();

  Serial.print("IP Address: ");

  Serial.println(ip);

  // print the received signal strength:

  long rssi = WiFi.RSSI();

  Serial.print("signal strength (RSSI):");

  Serial.print(rssi);

  Serial.println(" dBm");
}