#include <ESP8266WiFi.h>
#include <WiFiUdp.h>
#include <Ticker.h>

Ticker nameLookup;
char* packet = NULL;
unsigned short int packet_size;

WiFiUDP udp;

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  generateDnsQuery();

  Serial.println("");
  Serial.println(WiFi.localIP());

  udp.beginMulticast(WiFi.localIP(), IPAddress(224, 0, 0, 251), 5353);

}

void loop() {

  // Send mDNS request
  udp.beginPacketMulticast(IPAddress(224, 0, 0, 251), 5353, WiFi.localIP(),255);
  udp.write(packet, packet_size);
  udp.endPacket();
  delay(1);

  Serial.println("Sent: ");

  int cb = udp.parsePacket();
  if(cb>0){
      Serial.print("got udp packet from ");
      Serial.println(udp.remoteIP());
  }

  delay(1000);

}

void generateDnsQuery(){
    char header[13] = { 0x00, 0x00, // ID
                        0x00, 0x00, // FLAGS
                        0x00, 0x01, // QDCOUNT
                        0x00, 0x00, // ANCOUNT
                        0x00, 0x00, // NSCOUNT
                        0x00, 0x00, // ARCOUNT
                        0x00 };     // hostname length

    char trailer[11] = { 0x05, 0x6c, 0x6f, 0x63, 0x61, 0x6c, 0x00, //local + null terminator
                         0x00, 0x01,   // QDTYPE
                         0x00, 0x01};  // QCLASS

    unsigned short int hostname_len = strlen(hostname);
    packet_size = 24 + hostname_len;
    packet = new char[packet_size];


  // Forge the request packet
    header[12] = hostname_len;         // Set hostname length byte
    memcpy(packet, header, 13);
    memcpy(packet+13, hostname, hostname_len);
    memcpy(packet+13+hostname_len, trailer, 11);

}