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

#ifndef STASSID
#define STASSID "LIEA-Tx-Gx"
#define STAPSK "StrongPass123"
#endif

unsigned int localPort = 4321;

// buffers for receiving and sending data
char packetBuffer[UDP_TX_PACKET_MAX_SIZE + 1];  // buffer to hold incoming packet,
char AckBuffer[] = "acknowledged\r\n";        // a test string to send back...
char ReplyBuffer[UDP_TX_PACKET_MAX_SIZE + 1]; 

WiFiUDP MyUDP;

void setup() {
  Serial.begin(115200);
  WiFi.begin(STASSID, STAPSK);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print('.');
    delay(500);
  }
  Serial.print("Connected! IP address: ");
  Serial.println(WiFi.localIP());
  Serial.printf("UDP server on port %d\n", localPort);
  MyUDP.begin(localPort);
}

void loop() {

  int i = 0;
  
  // if there's data available, read a packet
  int packetSize = MyUDP.parsePacket();
  if (packetSize) {
    Serial.printf("Received packet of size %d from %s:%d\n    (to %s:%d)\n", packetSize, 
    MyUDP.remoteIP().toString().c_str(), MyUDP.remotePort(), 
    MyUDP.destinationIP().toString().c_str(), MyUDP.localPort());

    // read the packet into packetBufffer
    int n = MyUDP.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
    packetBuffer[n] = 0;
    Serial.println("Contents:");
    Serial.println(packetBuffer);

    // send a reply, to the IP address and port that sent us the packet we received
    MyUDP.beginPacket(MyUDP.remoteIP(), MyUDP.remotePort());
    MyUDP.write(AckBuffer);
    MyUDP.endPacket();

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

    sprintf(ReplyBuffer, "Hello %d from Rasp Pi W!\n\r", i++);
    MyUDP.write(ReplyBuffer);
    MyUDP.endPacket();
   
  }
}