mqttesp.h

#define WLAN_SSID       "..."
#define WLAN_PASS       "..."
#define WLAN_HOSTNAME   "gardenrelay-1"
#define IO_USERNAME  "j15e"
#define IO_KEY       "..."
#define FEED_PATH IO_USERNAME "/f/garden/"

#define SET_PIN 5
#define UNSET_PIN 4

#include <ESP8266WiFi.h>
#include <EthernetClient.h>
#include <SPI.h>
#include <PubSubClient.h>

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
  
  int state = payload[0];
  
  if(state == 1) {
    openRelay();
  } else {
    closeRelay();
  }
  Serial.println("");
}

WiFiClient client;
PubSubClient mqttclient(client);

void setup() {
  Serial.begin(115200);
  delay(100);

  // Close relay during boot
  closeRelay();
  
  // Connecting to WiFi network
  Serial.println();
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(WLAN_SSID);

  WiFi.hostname(WLAN_HOSTNAME);
  WiFi.begin(WLAN_SSID, WLAN_PASS);
  
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(120);
  }
  
  Serial.println("WiFi connected");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  Serial.print("Mac Address: ");
  Serial.println(WiFi.macAddress());

  // Connect to MQTT and subscribe to a path
  mqttclient.setServer("io.adafruit.com", 1883);
  mqttclient.setCallback(callback);
  if (mqttclient.connect("ESP8266Client", IO_USERNAME, IO_KEY)) {
    Serial.println("MQTT Connected");
    if(mqttclient.subscribe(FEED_PATH)) {   
       Serial.println("MQTT Subcribed to : ");
       Serial.println(FEED_PATH);
     }
  } else {
    Serial.println("MQTT Not connected : ");
    Serial.println(mqttclient.state());
  }
}

void loop() {
  mqttclient.loop();
  if (!mqttclient.connected()) {
    mqttclient.connect("ESP8266Client", IO_USERNAME, IO_KEY);
    mqttclient.subscribe(FEED_PATH);
  } else {
    if(mqttclient.publish(FEED_PATH, "1")) {
      Serial.println("Published!");
    } else {
      Serial.println("Not published!");
      Serial.println("MQTT State : ");
      Serial.println(mqttclient.state());
    };
  }
  Serial.println("MQTT State : ");
  Serial.println(mqttclient.state());
  delay(1000);
}

void openRelay() {
  analogWrite(SET_PIN, PWMRANGE);
  delay(15);
  analogWrite(SET_PIN, 0);
}

void closeRelay() {
  analogWrite(UNSET_PIN, PWMRANGE);
  delay(15);
  analogWrite(UNSET_PIN, 0);
 }