依赖 json工具
Arduino_JSON

#include <Arduino_JSON.h>
 
void setup() {
  Serial.begin(9600);
 
  // 创建一个 JSON 对象
  JSONVar myObject;
  myObject["name"] = "Arduino";
  myObject["version"] = 1.0;
 
  // 将 JSON 对象转换为字符串
  String jsonString = JSON.stringify(myObject);
  Serial.println(jsonString);
 
  // 解析 JSON 字符串
  JSONVar parsed = JSON.parse(jsonString);
 
  if (JSON.typeof(parsed) == "undefined") {
    Serial.println("Parsing failed!");
    return;
  }
 
  Serial.print("Name: ");
  Serial.println((const char*) parsed["name"]);
  Serial.print("Version: ");
  Serial.println((double) parsed["version"]);
}

ArduinoJson

#include <ArduinoJson.h>

void setup() {
  Serial.begin(9600);
  const char* json = "{\"name\":\"John\",\"age\":30,\"city\":\"New York\"}";
  DynamicJsonDocument doc(1024);
  DeserializationError error = deserializeJson(doc, json);
  if (error) {
    Serial.print("Failed to deserialize JSON: ");
    Serial.println(error.f_str());
    return;
  }
  const char* name = doc["name"];
  int age = doc["age"];
  const char* city = doc["city"];
  Serial.print("Name: ");
  Serial.println(name);
  Serial.print("Age: ");
  Serial.println(age);
  Serial.print("City: ");
  Serial.println(city);
}

完整示例

#include "header.cpp"
int count;    // Ticker计数用变量
int pin = 0;  // 设置一个变量代表控制继电器开关的GPIO
// int LED_BUILTIN = 2; led灯开关
//  JSON 对象 wifi配置
JSONVar wifiConf;
// json 对象 mqtt配置
JSONVar mqttConf;
// 定时器
Ticker ticker;

// WiFi and MQTT client initialization
BearSSL::WiFiClientSecure espClient;
PubSubClient mqtt_client(espClient);

// Function declarations
void connectToWiFi();

void connectToMQTT();

void syncTime();

void mqttCallback(char *topic, byte *payload, unsigned int length);
// wifi 账号密码
void initWifiConfig() {
  wifiConf["user"] = "hy1";
  wifiConf["password"] = "13363641456";
}
// mqtt 配置
void initMqttConfig() {
  mqttConf["mqtt_port"] = 8883;
  // 去 EMQX 官网注册账号可以申请免费额度
  mqttConf["mqtt_broker"] = "n9a7eff0.ala.cn-hangzhou.emqxsl.cn";
  // 订阅主题
  mqttConf["mqtt_subscribe_topic"] = "emqx/esp8266";
  // 发布主题
  mqttConf["mqtt_publish_topic"] = "emqx/esp8266";
  // 用户名
  mqttConf["mqtt_username"] = "test";
  // 密码
  mqttConf["mqtt_password"] = "test123456";
 // NTP Server settings
  mqttConf["ntp_server"] = "pool.ntp.org";// Recommended NTP server for users in China
  mqttConf["gmt_offset_sec"] = 0; // GMT offset in seconds (adjust for your time zone)
  mqttConf["daylight_offset_sec"] = 0;// Daylight saving time offset in seconds
  // 每间隔多少秒发布一次当前状态
  mqttConf["push_state_m"] = 20;
  // SSL certificate for MQTT broker
// Load DigiCert Global Root G2, which is used by EMQX Public Broker: broker.emqx.io
// static const char ca_cert[]
// PROGMEM = R"EOF()EOF";
  // 服务端的 ssl/tls ca证书
  mqttConf["ca_cert"] = R"EOF(
-----BEGIN CERTIFICATE-----
MIIDrzCCApegAwIBAgIQCDvgVpBCRrGhdWrJWZHHSjANBgkqhkiG9w0BAQUFADBh
MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3
d3cuZGlnaWNlcnQuY29tMSAwHgYDVQQDExdEaWdpQ2VydCBHbG9iYWwgUm9vdCBD
QTAeFw0wNjExMTAwMDAwMDBaFw0zMTExMTAwMDAwMDBaMGExCzAJBgNVBAYTAlVT
MRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5j
b20xIDAeBgNVBAMTF0RpZ2lDZXJ0IEdsb2JhbCBSb290IENBMIIBIjANBgkqhkiG
9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4jvhEXLeqKTTo1eqUKKPC3eQyaKl7hLOllsB
CSDMAZOnTjC3U/dDxGkAV53ijSLdhwZAAIEJzs4bg7/fzTtxRuLWZscFs3YnFo97
nh6Vfe63SKMI2tavegw5BmV/Sl0fvBf4q77uKNd0f3p4mVmFaG5cIzJLv07A6Fpt
43C/dxC//AH2hdmoRBBYMql1GNXRor5H4idq9Joz+EkIYIvUX7Q6hL+hqkpMfT7P
T19sdl6gSzeRntwi5m3OFBqOasv+zbMUZBfHWymeMr/y7vrTC0LUq7dBMtoM1O/4
gdW7jVg/tRvoSSiicNoxBN33shbyTApOB6jtSj1etX+jkMOvJwIDAQABo2MwYTAO
BgNVHQ8BAf8EBAMCAYYwDwYDVR0TAQH/BAUwAwEB/zAdBgNVHQ4EFgQUA95QNVbR
TLtm8KPiGxvDl7I90VUwHwYDVR0jBBgwFoAUA95QNVbRTLtm8KPiGxvDl7I90VUw
DQYJKoZIhvcNAQEFBQADggEBAMucN6pIExIK+t1EnE9SsPTfrgT1eXkIoyQY/Esr
hMAtudXH/vTBH1jLuG2cenTnmCmrEbXjcKChzUyImZOMkXDiqw8cvpOp/2PV5Adg
06O/nVsJ8dWO41P0jmP6P6fbtGbfYmbW0W5BjfIttep3Sp+dWOIrWcBAI+0tKIJF
PnlUkiaY4IBIqDfv8NZ5YBberOgOzW6sRBc4L0na4UU+Krk2U886UAb3LujEV0ls
YSEY1QSteDwsOoBrp+uvFRTp2InBuThs4pFsiv9kuXclVzDAGySj4dzp30d8tbQk
CAUw7C29C79Fv1C5qfPrmAESrciIxpg0X40KPMbp1ZWVbd4=
-----END CERTIFICATE-----
)EOF";

}
void initConfig() {
  initWifiConfig();
  initMqttConfig();
}
void tickerCount() {
  count++;
}
void setup() {
  Serial.begin(115200);
  initConfig();
  pinMode(LED_BUILTIN, OUTPUT);  // 这里换成变量
  pinMode(pin, OUTPUT);
  digitalWrite(pin, LOW);  // GPIO0 低电平，吸合继电器，作为初始状态

  // Ticker定时对象
  ticker.attach(1, tickerCount);
  //设置ESP8266工作模式为无线终端模式
  WiFi.mode(WIFI_STA);
  connectToWiFi();
  syncTime();  // X.509 validation requires synchronization time
  mqtt_client.setServer((const char *)mqttConf["mqtt_broker"], (const int)mqttConf["mqtt_port"]);
  mqtt_client.setCallback(mqttCallback);
  connectToMQTT();
}

void connectToWiFi() {
  WiFi.begin((const char *)wifiConf["user"], (const char *)wifiConf["password"]);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  Serial.println("Connected to WiFi");
}

void syncTime() {
  configTime((const long)mqttConf["gmt_offset_sec"], (const int)mqttConf["daylight_offset_sec"], (const char *)mqttConf["ntp_server"]);
  Serial.print("Waiting for NTP time sync: ");
  while (time(nullptr) < 8 * 3600 * 2) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println("Time synchronized");
  struct tm timeinfo;
  if (getLocalTime(&timeinfo)) {
    Serial.print("Current time: ");
    Serial.println(asctime(&timeinfo));
  } else {
    Serial.println("Failed to obtain local time");
  }
}

void connectToMQTT() {
  BearSSL::X509List serverTrustedCA((const char *)mqttConf["ca_cert"]);
  espClient.setTrustAnchors(&serverTrustedCA);
  JSONVar mqttMsg;
  while (!mqtt_client.connected()) {
    // String client_id = "esp8266-client-" + String(WiFi.macAddress());
    mqttMsg["client_id"] = "esp8266-client-" + String(WiFi.macAddress());
    Serial.printf("Connecting to MQTT Broker as %s.....\n", ((String)mqttMsg["client_id"]).c_str());
    if (mqtt_client.connect(((String)mqttMsg["client_id"]).c_str(), (const char *)mqttConf["mqtt_username"], (const char *)mqttConf["mqtt_password"])) {
      Serial.println("Connected to MQTT broker");
      mqttMsg["msg"] = "Hi EMQX I'm ESP8266";
      mqttMsg["key"] = "connect";
      mqtt_client.subscribe((const char *)mqttConf["mqtt_subscribe_topic"]);
      // Publish message upon successful connection
      // 将 JSON 对象转换为字符串
      String jsonString = JSON.stringify(mqttMsg);
      mqtt_client.publish((const char *)mqttConf["mqtt_publish_topic"], jsonString.c_str());
    } else {
      char err_buf[128];
      espClient.getLastSSLError(err_buf, sizeof(err_buf));
      Serial.print("Failed to connect to MQTT broker, rc=");
      Serial.println(mqtt_client.state());
      Serial.print("SSL error: ");
      Serial.println(err_buf);
      delay(5000);
    }
  }
}
// 发布上报针脚状态信息
void pubMQTTmsg() {
  JSONVar mqttMsg;
  // 建立发布主题。
  // 定时向服务器主题发布当前GPIO0引脚状态
  String state;
  if (digitalRead(0)) {
    mqttMsg["state"] = false;  // 高电平断开继电器
  } else {
    mqttMsg["state"] = true;  // 低电平吸合继电器
  }
  String jsonString = JSON.stringify(mqttMsg);

  // 实现ESP8266向主题发布信息
  if (mqtt_client.publish((const char *)mqttConf["mqtt_publish_topic"], jsonString.c_str())) {
    Serial.print("Publish Topic: ");
    Serial.println((const char *)mqttConf["mqtt_publish_topic"]);
    Serial.print("Publish message: ");
    Serial.println(jsonString.c_str());
  } else {
    Serial.println("Message Publish Failed.");
  }
}

void mqttCallback(char *topic, byte *payload, unsigned int length) {
  Serial.print("Message received on topic: ");
  Serial.print(topic);
  Serial.print("]: ");
  // 将获取到的pyte类payload消息转换为String类型的data
  String jsonString = "";
  for (int i = 0; i < length; i++) {
    jsonString = jsonString + (char)payload[i];
  }
  Serial.println(jsonString);
  // mqttRes=
  // 解析 JSON 字符串
  JSONVar parsed = JSON.parse(jsonString);

  if (JSON.typeof(parsed) == "undefined") {
    Serial.println("Parsing failed!");
    return;
  }
  if (parsed["switch"] != null) {
    Serial.println((String)parsed["switch"]);
    if ((String)parsed["switch"] == "1") {  // 如果收到的信息为"1"，注意双引号为String，单引号为char
      digitalWrite(LED_BUILTIN, LOW);  // 则点亮LED。
      digitalWrite(pin, LOW);               // GPIO0 低电平，吸合继电器
    } else {
      digitalWrite(LED_BUILTIN, HIGH); // 否则熄灭LED。
      digitalWrite(pin, HIGH);  // GPIO0 高电平，断开继电器
    }
  }
}

// 状态持续函数，一直重复执行
void loop() {

  if (!mqtt_client.connected()) {
    // 建立链接
    connectToMQTT();

  } else {
    // 每隔3秒钟发布一次信息，一般用于状态报告
    if (count >= (int)mqttConf["push_state_m"]) {
      pubMQTTmsg();
      count = 0;
    }
    //  心跳
    mqtt_client.loop();
  }
}
// 使用
// 服务端向订阅主题发布 消息内容 {"switch": "1"} 1是开灯，否则是关灯

header.h

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <time.h>
#include <Ticker.h>
#include <Arduino_JSON.h>