Steps to implement remote temperature monitoring and control using PHP and MQTT

Steps to implement remote temperature monitoring and control using PHP and MQTT

With the rapid development of Internet of Things technology, remote monitoring and control have become common needs in our daily lives. This article will introduce how to use PHP and MQTT protocols to implement remote temperature monitoring and control. We will use a temperature sensor based on ESP8266 as an example and send the temperature data to the remote server through the MQTT protocol. At the same time, the remote server can send control instructions to the ESP8266 through the MQTT protocol. Here are the steps to implement.

Step 1: Configure MQTT server
First, we need to install and configure an MQTT server to facilitate communication between the device and the server. Here we use the open source Mosquitto MQTT server as an example. You can choose other MQTT servers according to your needs. After the installation is complete, you need to configure the IP address, port number, user name, password and other related information of the MQTT server, and create a Topic for communication between the device and the server.

Step 2: Configure ESP8266
Install an MQTT library on ESP8266. Here we use the phpMQTT library as an example. You can install this library through the Arduino IDE's library management interface. After that, you need to configure the WiFi connection and MQTT server-related information in the code, including WiFi name and password, as well as the IP address, port number, user name, password and other information of the MQTT server. At the same time, you need to configure the topic of the device. Here we can name it "temperature" to transfer temperature data.

The following is a simple ESP8266 code example:

#include <ESP8266WiFi.h>
#include <phpMQTT.h>

const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";
const char* mqtt_server = "MQTT_SERVER_IP";
const char* topic = "temperature";

WiFiClient espClient;
phpMQTT mqtt;

float temperature = 0;

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

  WiFi.begin(ssid, 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 callback(char* topic, byte* payload, unsigned int length) {
  // handle incoming MQTT messages here
}

void reconnect() {
  // Loop until we're reconnected
  while (!mqtt.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (mqtt.connect("ESP8266Client")) {
      Serial.println("connected");
      mqtt.subscribe(topic);
    } else {
      Serial.print("failed, rc=");
      Serial.print(mqtt.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void setup() {
  Serial.begin(115200);
  setup_wifi();
  mqtt.begin(mqtt_server, 1883, espClient);
  mqtt.onMessage(callback);
}

void loop() {
  if (!mqtt.connected()) {
    reconnect();
  }
  mqtt.loop();

  // simulate reading temperature from sensor
  temperature = random(20, 40);

  // convert temperature to string for MQTT publishing
  char tmp[10];
  sprintf(tmp, "%.2f", temperature);
  
  // publish temperature to MQTT topic
  mqtt.publish(topic, tmp);
  
  delay(2000);
}

Step three: Configure PHP server
On the remote server, we need to install and configure an MQTT client library, here we use phpMQTT library. You can install this library through Composer. After that, configure the relevant information of the MQTT server in the PHP code, including IP address, port number, user name, password, etc. At the same time, you need to subscribe to the temperature data sent by the device so that you can monitor temperature changes in real time. Here is a simple PHP code example:

<?php

require("phpMQTT.php");

$mqtt_server = "MQTT_SERVER_IP";
$mqtt_port = 1883;
$mqtt_user = "your_MQTT_username";
$mqtt_password = "your_MQTT_password";
$mqtt_topic = "temperature";

$client_id = "PHPServer";

$mqtt = new phpMQTT($mqtt_server, $mqtt_port, $client_id);

if(!$mqtt->connect(true, NULL, $mqtt_user, $mqtt_password)){
    exit(1);
}

$topics[$mqtt_topic] = array("qos"=>0, "function"=>"receiveTemperature");
$mqtt->subscribe($topics, 0);

while($mqtt->proc()){
}

$mqtt->close();

function receiveTemperature($topic, $payload){
    // handle incoming temperature data here
    $temperature = floatval($payload);
    // do something with the temperature data, such as storing it in a database or triggering a notification
}

?>

Step Four: Temperature Monitoring and Control
Now you can connect the ESP8266 to a power source and view the operation of the device in the serial monitor. ESP8266 will regularly read the value of the temperature sensor and publish it to the specified topic through the MQTT protocol. At the same time, the PHP server will subscribe to this topic and perform corresponding processing based on the received temperature data, such as storing it in the database or triggering an alarm.

On the basis of temperature monitoring, you can also implement temperature control function. You can add an MQTT publishing function to your PHP code to send control instructions to the ESP8266. You can trigger control instructions through the web interface, App or other methods according to your needs, and send the instructions to the ESP8266 through the MQTT protocol. ESP8266 can perform corresponding control operations according to the received instructions.

In summary, by using PHP and MQTT protocols, we can easily implement remote temperature monitoring and control functions. This method can be applied to various scenarios, such as indoor temperature monitoring, greenhouse temperature control, etc. Hope this article can be helpful to you.

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