STA接收UDP訊息並回傳OK的程式碼

#include <ESP8266WiFi.h>
#include <WiFiUdp.h>
#define WIFI_SSID "ESP8266"
#define WIFI_PASS "password"
#define UDP_PORT 1026
WiFiUDP UDP;
char packet[255];
char reply[] = "OK";
   
void setup() {
  Serial.begin(9600);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  Serial.print("Connecting to ");
  Serial.print(WiFi.SSID());
  while (WiFi.status() != WL_CONNECTED){
    delay(100);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected! IP address: ");
  Serial.println(WiFi.localIP());
  UDP.begin(UDP_PORT);
}
   
void loop() {
  if(int packetSize = UDP.parsePacket()){//有接收到訊息的時候packetSize就會大於0，使條件式成立
    if (int len = UDP.read(packet, 255)){ 
      packet[len] = '\0';         // 在訊息後面補上\0，讓arduino知道字串到哪裡結束
    }
    Serial.print("資料內容: ");
    Serial.println(packet);
    //回傳訊息
    UDP.beginPacket(UDP.remoteIP(),UDP.remotePort());
    UDP.write(reply);
    UDP.endPacket();
  }
}