AsyncUDPMulticastServer.ino

#include "WiFi.h"
#include "AsyncUDP.h"

const char *ssid = "***********";
const char *password = "***********";

AsyncUDP udp;

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  if (WiFi.waitForConnectResult() != WL_CONNECTED) {
    Serial.println("WiFi Failed");
    while (1) {
      delay(1000);
    }
  }
  if (udp.listenMulticast(IPAddress(239, 1, 2, 3), 1234)) {
    Serial.print("UDP Listening on IP: ");
    Serial.println(WiFi.localIP());
    udp.onPacket([](AsyncUDPPacket packet) {
      Serial.print("UDP Packet Type: ");
      Serial.print(packet.isBroadcast() ? "Broadcast" : packet.isMulticast() ? "Multicast" : "Unicast");
      Serial.print(", From: ");
      Serial.print(packet.remoteIP());
      Serial.print(":");
      Serial.print(packet.remotePort());
      Serial.print(", To: ");
      Serial.print(packet.localIP());
      Serial.print(":");
      Serial.print(packet.localPort());
      Serial.print(", Length: ");
      Serial.print(packet.length());
      Serial.print(", Data: ");
      Serial.write(packet.data(), packet.length());
      Serial.println();
      //reply to the client
      packet.printf("Got %u bytes of data", packet.length());
    });
    //Send multicast
    udp.print("Hello!");
  }
}

void loop() {
  delay(1000);
  //Send multicast
  udp.print("Anyone here?");
}