http://arduino.esp8266.com/stable/package_esp8266com_index.json, https://dl.espressif.com/dl/package_esp32_index.json

#include "Arduino.h"
#include "EspMQTTClient.h" /* https://github.com/plapointe6/EspMQTTClient */
                           /* https://github.com/knolleary/pubsubclient */
#define PUB_DELAY (5 * 1000) /* 5 seconds */
EspMQTTClient client(
  "<wifi-ssid>",
  "<wifi-password>",
  "dev.rightech.io",
  "<ric-mqtt-client-id>"
);
void setup() {
  Serial.begin(9600);
}
void onConnectionEstablished() {
  client.subscribe("base/relay/led1", [] (const String &payload)  {
    Serial.println(payload);
  });
}
long last = 0;
void publishTemperature() {
  long now = millis();
  if (client.isConnected() && (now - last > PUB_DELAY)) {
    client.publish("base/state/temperature", String(random(20, 30)));
    client.publish("base/state/humidity", String(random(40, 90)));
    last = now;
  }
}
void loop() {
  client.loop();
  publishTemperature();
}