//=================Code Begin=================
#include <WiFi.h>
#include "AsyncUDP.h"
#define debug Serial
//Wifi Network Connection Parameters for STA interface
const char* wifi_network_ssid = "My_Home_Network";
const char* wifi_network_password = "My_Home_Network_Pass";
//Wifi Network Connection Parameters for STA interface
const char *soft_ap_ssid = "My_Esp_AP";
const char *soft_ap_password = "My_Esp_AP_Pass";
AsyncUDP udp;
volatile boolean pkt_received=false;
unsigned long time_last, time_now;
void setup() {
 debug.begin(115200);
 
 WiFi.mode(WIFI_MODE_APSTA);
 debug.printf("Starting AP: '%s' \n", soft_ap_ssid);
 WiFi.softAP(soft_ap_ssid, soft_ap_password);
 debug.printf("Connecting to WiFi over STA I/F to network '%s'\n", wifi_network_ssid);
 WiFi.begin(wifi_network_ssid, wifi_network_password);
 
 //TODO: Add a timeout logic
 while (WiFi.status() != WL_CONNECTED) {
 delay(500);
 debug.print(".");
 }
 debug.printf("\nConnected to WiFi Station network '%s'. IP: %s\n", wifi_network_ssid, WiFi.localIP().toString().c_str());
 
 debug.printf("AP Interface IP Address: '%s'\n", WiFi.softAPIP().toString().c_str());
 debug.print("TCPIP_ADAPTER_IF_STA="); debug.println(TCPIP_ADAPTER_IF_STA);
 debug.print("TCPIP_ADAPTER_IF_AP="); debug.println(TCPIP_ADAPTER_IF_AP);
 debug.print("TCPIP_ADAPTER_IF_ETH="); debug.println(TCPIP_ADAPTER_IF_ETH);
 debug.print("TCPIP_ADAPTER_IF_TEST="); debug.println(TCPIP_ADAPTER_IF_TEST);
 debug.print("TCPIP_ADAPTER_IF_MAX="); debug.println(TCPIP_ADAPTER_IF_MAX);
 if(udp.listenMulticast(IPAddress(239,1,2,3), 1234, TCPIP_ADAPTER_IF_AP)) { //Start listening for UDP Multicast on AP interface only
 debug.printf("UDP Listening on IP: '%s'\n", WiFi.softAPIP().toString().c_str());
 udp.onPacket([](AsyncUDPPacket packet) {
 pkt_received=true;
 Serial.printf("%lu ms:", millis());
 Serial.print("UDP Packet Received. Type: ");
 Serial.print(packet.isBroadcast()?"Broadcast":packet.isMulticast()?"Multicast":"Unicast");
 Serial.print(", Received at i/f: ");
 Serial.print(packet.interface()); //0: STA Interface. 1: AP Interface
 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());
 });
 }
}
void loop() {
 unsigned long time_diff;
 
 //Switch on LED when UDP multicast packet is received
 if (pkt_received) {
 digitalWrite(LED_BUILTIN, HIGH);
 time_last = millis();
 pkt_received=false;
 }
 //Switch off the LED after 2 seconds
 time_now = millis();
 time_diff = time_now - time_last;
 
 if (time_diff > 2000){
 digitalWrite(LED_BUILTIN, LOW);
 }
}
//=================Code End=================

//=================Output Begin=================
Starting AP: 'My_Esp_AP'
Connecting to WiFi Station network 'My_Home_Network'
Connected to WiFi Station network 'My_Home_Network'. IP: 192.168.5.188
AP Interface IP Address: '192.168.4.1'
TCPIP_ADAPTER_IF_STA=0
TCPIP_ADAPTER_IF_AP=1
TCPIP_ADAPTER_IF_ETH=2
TCPIP_ADAPTER_IF_TEST=3
TCPIP_ADAPTER_IF_MAX=4
UDP Listening on IP: '192.168.4.1'
13859ms: UDP Packet Received. Type: Multicast, Received at i/f: 1, From: 192.168.4.2:49795, To: 239.1.2.3:1234, Length: 6, Data: hello
31183ms: UDP Packet Received. Type: Multicast, Received at i/f: 0, From: 192.168.5.165:49795, To: 239.1.2.3:1234, Length: 6, Data: hello
//=================Output End=================