Notes

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
char wifi_ssid[] = "SUPERONLINE_WiFi_5364"; // your network SSID (name)
char wifi_password[] = "nRbXNCzPQ54U"; // your network password

char * mqtt_server = "37.148.209.175";
int mqtt_port = 1993;
char * mqtt_user = "root";
char * mqtt_password = "Vr9Fr6Ge8";

#define in_topic "temp"
#define out_topic "temp"
// Replace by 2 if you aren't enable to use Serial Monitor... Don't forget to Rewire R1 to GPIO2!
#define in_led 0

WiFiClient espClient;
PubSubClient client;

void setup() {
Serial.begin(115200);
setup_wifi();
client.setClient(espClient);
client.setServer(mqtt_server, mqtt_port);
client.setCallback(callback);

// initialize digital pin LED_BUILTIN as an output.
pinMode(in_led, OUTPUT);
digitalWrite(in_led, HIGH);
}

void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
Serial.println();
Serial.print("Connecting to ");
Serial.println(wifi_ssid);

WiFi.begin(wifi_ssid, wifi_password);

while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}

Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
}

void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Attempt to connect
// If you do not want to use a username and password, change next line to
// if (client.connect("ESP8266Client")) {
if (client.connect("ESP8266Client", mqtt_user, mqtt_password)) {
Serial.println("connected");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}

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++) {
char receivedChar = (char)payload[i];
Serial.print(receivedChar);
if (receivedChar == '0')
digitalWrite(in_led, LOW);
if (receivedChar == '1')
digitalWrite(in_led, HIGH);
}
Serial.println();
}

void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
// Publishes a random 0 and 1 like someone switching off and on randomly (random(2))
client.publish(out_topic, "TEMP", true);
delay(1000);
client.subscribe(in_topic);
delay(1000);
}