IoT setup

ESP8266

Make sure you have the Arduino IDE installed on your machine.
Upload either a .ino file:
1. Install PubSubClient
2. And upload this to your module, making sure to assign your wifi network name (SSID) and password (PASSWORD) as well as the topic you want this module to be subscribed to (TOPIC):
#include <ESP8266WiFi.h>
#include <PubSubClient.h>

const char *SSID = "my wifi network";
const char *PASSWORD = "the password is written on the router";

const char *BROKER_MQTT = "localhost";
int BROKER_PORT = 1883;

const char *TOPIC = "";

void initPins();
void initSerial();
void initWiFi();
void initMQTT();

WiFiClient espClient;
PubSubClient MQTT(espClient);

void setup()
{
initPins();
initSerial();
initWiFi();
initMQTT();
}

void loop()
{
if (!MQTT.connected())
{
reconnectMQTT();
}
recconectWiFi();
MQTT.loop();
}

void initPins()
{
pinMode(D5, OUTPUT);
digitalWrite(D5, 0);
}

void initSerial()
{
Serial.begin(115200);
}
void initWiFi()
{
delay(10);
Serial.println("Connecting to: " + String(SSID));

WiFi.begin(SSID, PASSWORD);
while (WiFi.status() != WL_CONNECTED)
{
delay(100);
Serial.print(".");
}
Serial.println();
Serial.print("Connecting to " + String(SSID) + " | IP => ");
Serial.println(WiFi.localIP());
}

void initMQTT()
{
MQTT.setServer(BROKER_MQTT, BROKER_PORT);
MQTT.setCallback(mqtt_callback);
}

void mqtt_callback(char *topic, byte *payload, unsigned int length)
{

String message;
for (int i = 0; i < length; i++)
{
char c = (char)payload[i];
message += c;
}
Serial.println("Topic => " + String(topic) + " | Value => " + String(message));
if (message == "1")
{
digitalWrite(D5, 1);
}
else
{
digitalWrite(D5, 0);
}
Serial.flush();
}

void reconnectMQTT()
{
while (!MQTT.connected())
{
Serial.println("Trying to connect to the MQTT Broker: " + String(BROKER_MQTT));
if (MQTT.connect("ESP8266-ESP12-E"))
{
Serial.println("Connected");
MQTT.subscribe(TOPIC);
}
else
{
Serial.println("Failed to reconnect");
Serial.println("Trying to reconnect in 2 seconds");
delay(2000);
}
}
}

void recconectWiFi()
{
while (WiFi.status() != WL_CONNECTED)
{
delay(100);
Serial.print(".");
}
}
Or a .lua file:
1. Make sure to pass your network name as the third parameter (replacing "username") of the Client method, and your network password as the fourth parameter (replacing "password") and to assing the topic you want to subscribe this module to to the topic variable:
-- initiate the mqtt client and set keepalive timer to 120sec
mqtt = mqtt.Client("client_id", 120, "username", "password")
local topic = ""

mqtt:on("connect", function(con) print ("connected") end)
mqtt:on("offline", function(con) print ("offline") end)

-- on receive message
mqtt:on("message", function(conn, topic, data)
print(topic .. ":" )
if data ~= nil then
print(data)
end
end)

mqtt:connect("hostname", port, 0, function(conn)
print("connected")
-- subscribe topic with qos = 0
mqtt:subscribe(topic, 0, function(conn)
-- publish a message with data = my_message, QoS = 0, retain = 0
mqtt:publish("my_topic","my_message",0,0, function(conn)
print("sent")
end)
end)
end)

ESP8266#

ESP8266