Comunicación UDP mediante Ethernet en un ESP32 PLC

// Simple UDP communication for controlling a LED
// Commands: Start, LedON, LedOFF

#include <ethernet.h>
#include <ethernetudp.h>

// 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(10, 42, 0, 20);

unsigned int localPort = 8888;      // local port to listen on
unsigned int replyPort = 8889;      // port to send response to

char packetBuffer[UDP_TX_PACKET_MAX_SIZE];  // buffer for receiving incoming data

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

bool ledStatus = LOW;

// Response function
String responseUdp(String incoming_message){
  incoming_message = incoming_message.substring(0,incoming_message.length()-1);
  if (incoming_message=="Start"){ledStatus=HIGH; return "ACK0";}
  else if (incoming_message=="LedOn"){ledStatus=HIGH; return "ACK1";}
  else if (incoming_message == "LedOff"){ledStatus=LOW; return "ACK2";}
  else return "Unrecognised Command";
}

void setup() {
  // Serial
  Serial.begin(9600);
  while (!Serial) {;}
  Serial.println("Serial ready");

  // Ethernet
  Ethernet.begin(mac, ip);
  // Check for Ethernet hardware
  if (Ethernet.hardwareStatus() == EthernetNoHardware) {
    Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware. :(");
    while (true) {
      delay(1); // do nothing, no point running without Ethernet hardware
    }
  }
  if (Ethernet.linkStatus() == LinkOFF) {
    Serial.println("Ethernet cable is not connected.");
  }
  Serial.println("Ethernet ready");

  // Start UDP
  Udp.begin(localPort);
  Serial.println("UDP ready");
}

void loop() {
  // if there's data available, read a packet
  int packetSize = Udp.parsePacket();
  if (packetSize) {
    // read the packet into packetBufffer
    Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
    
    // Packet info
    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());
    Serial.print("Contents:");
    Serial.println(packetBuffer); //*/

    // Process packet and generate response
    String reply = responseUdp(packetBuffer);
    
    // send a reply to the IP address that sent us the packet we received to a port of our choice
    int reply_port = replyPort;     // Port to send msg back to. Switch to Udp.remotePort() to reply to the transmitting port
    Udp.beginPacket(Udp.remoteIP(), reply_port);
    
    Serial.println("Sending message \""+reply+"\" back to port: "+String(reply_port));
    reply+="\n";
    const char* udp_reply = reply.c_str();
    Udp.write(udp_reply);
    Udp.endPacket();  //*/
  }
  delay(10);
  if (ledStatus) {
    digitalWrite(Q0_0, HIGH);
  }
  else
  {
    digitalWrite(Q0_0, LOW);
  }
}