add a demo too!

examples/adafruitio_anon_time_esp8266/adafruitio_anon_time_esp8266.ino

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+/***************************************************
+  Adafruit MQTT Library ESP8266 Adafruit IO Anonymous Time Query
+
+  Must use the latest version of ESP8266 Arduino from:
+    https://github.com/esp8266/Arduino
+
+  Works great with Adafruit's Huzzah ESP board & Feather
+  ----> https://www.adafruit.com/product/2471
+  ----> https://www.adafruit.com/products/2821
+
+  Adafruit invests time and resources providing this open source code,
+  please support Adafruit and open-source hardware by purchasing
+  products from Adafruit!
+
+  Written by Adafruit Industries.
+  MIT license, all text above must be included in any redistribution
+ ****************************************************/
+#include <ESP8266WiFi.h>
+#include "Adafruit_MQTT.h"
+#include "Adafruit_MQTT_Client.h"
+
+/************************* WiFi Access Point *********************************/
+#define WLAN_SSID       "network"
+#define WLAN_PASS       "password"
+
+/************************* Adafruit.io Setup *********************************/
+#define AIO_SERVER      "io.adafruit.com"
+#define AIO_SERVERPORT  8883
+
+WiFiClientSecure client;
+Adafruit_MQTT_Client mqtt(&client, AIO_SERVER, AIO_SERVERPORT);
+
+Adafruit_MQTT_Subscribe timefeed = Adafruit_MQTT_Subscribe(&mqtt, "time/seconds");
+
+// set timezone offset from UTC
+int timeZone = -4; // UTC - 4 eastern daylight time (nyc)
+int interval = 4; // trigger every X hours
+
+int last_min = -1;
+
+void timecallback(uint32_t current) {
+  // adjust to local time zone
+  current += (timeZone * 60 * 60);
+  int curr_hour = (current / 60 / 60) % 24;
+  int curr_min  = (current / 60 ) % 60;
+  int curr_sec  = (current) % 60;
+
+  Serial.print("Time: "); 
+  Serial.print(curr_hour); Serial.print(':'); 
+  Serial.print(curr_min); Serial.print(':'); 
+  Serial.println(curr_sec);
+  
+  // only trigger on minute change
+  if(curr_min != last_min) {
+    last_min = curr_min;
+    
+    Serial.println("This will print out every minute!");
+  }
+}
+
+void setup() {
+
+  Serial.begin(115200);
+  delay(10);
+
+  Serial.print(F("\nAdafruit IO anonymous Time Demo"));
+
+  WiFi.begin(WLAN_SSID, WLAN_PASS);
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+    Serial.print(F("."));
+  }
+  Serial.println(F(" WiFi connected."));
+
+  timefeed.setCallback(timecallback);
+  mqtt.subscribe(&timefeed);
+
+}
+
+void loop() {
+
+  // Ensure the connection to the MQTT server is alive (this will make the first
+  // connection and automatically reconnect when disconnected).  See the MQTT_connect
+  // function definition further below.
+  MQTT_connect();
+
+  // wait 10 seconds for subscription messages
+  // since we have no other tasks in this example.
+  mqtt.processPackets(10000);
+
+  // keep the connection alive
+  mqtt.ping();
+
+}
+
+// Function to connect and reconnect as necessary to the MQTT server.
+// Should be called in the loop function and it will take care if connecting.
+void MQTT_connect() {
+  int8_t ret;
+
+  // Stop if already connected.
+  if (mqtt.connected()) {
+    return;
+  }
+
+  Serial.print("Connecting to MQTT... ");
+
+  uint8_t retries = 3;
+  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
+       Serial.println(mqtt.connectErrorString(ret));
+       Serial.println("Retrying MQTT connection in 5 seconds...");
+       mqtt.disconnect();
+       delay(5000);  // wait 5 seconds
+       retries--;
+       if (retries == 0) {
+         // basically die and wait for WDT to reset me
+         while (1);
+       }
+  }
+
+  Serial.println("MQTT Connected!");
+}