MQTT Basics: Pub/Sub & Keepalive

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#include <WiFi.h>

#include <PubSubClient.h>

WiFiClient espClient;
PubSubClient mqtt(espClient);
void cb(char * t, byte * p, unsigned int l) {
  /* handle msg */ }
void reconnect() {
  while (!mqtt.connected()) {
    mqtt.connect("esp32");
    mqtt.subscribe("home/cmd");
  }
}
void setup() {
  /* WiFi */
  mqtt.setServer("broker.hivemq.com", 1883);
  mqtt.setCallback(cb);
}
void loop() {
  if (!mqtt.connected()) reconnect();
  mqtt.loop();
  mqtt.publish("home/status", "ok");
  delay(2000);
}