PHP and MQTT: Building a remote energy monitoring and management system

PHP and MQTT: Building a remote energy monitoring and management system

Introduction
With the growth of energy demand and the enhancement of environmental awareness, establishing a remote energy monitoring and management system has become more and more important. . This kind of system can perform energy-saving management by monitoring energy usage in real time, and can adjust energy usage through remote control, thereby reducing energy waste and carbon footprint. In this article, we will explore how to build a remote energy monitoring and management system using PHP and MQTT protocols, and provide some code examples for reference.

1. Introduction to MQTT
   MQTT (Message Queuing Telemetry Transport) is a lightweight publish/subscribe message transmission protocol suitable for devices with limited network bandwidth and computing resources. It uses TCP/IP protocol for communication, supports push mode, and has low latency and high reliability.
2. Building MQTT Server
   First, we need to build an MQTT server to handle communication between the device and the application. This can be achieved using open source MQTT servers such as Mosquitto. Below is a basic Mosquitto server configuration example.

sudo apt-get install mosquitto
sudo systemctl enable mosquitto
sudo systemctl start mosquitto

3. PHP MQTT extension
   To use the MQTT protocol in PHP, we need to install an MQTT extension. You can choose to use the mosquitto or phpMQTT extension. Below is sample code using the phpMQTT extension.

require("phpMQTT.php");

$server = "mqtt.example.com";
$port = 1883;
$client_id = "phpMQTT-subscriber";

$mqtt = new phpMQTT($server, $port, $client_id);

if ($mqtt->connect(true, NULL, "username", "password")) {
    $topics = array("energy/usage/#" => array("qos" => 0, "function" => "processMessage"));
    $mqtt->subscribe($topics, 0);
    while ($mqtt->proc()) {
    }
    $mqtt->close();
} else {
    echo "Failed to connect to MQTT server.";
}

function processMessage($topic, $message) {
    echo "Received message on topic: $topic
";
    echo "Message: $message
";
    // 在这里可以编写处理MQTT消息的代码逻辑
}

In the above example, we first created a phpMQTT object and connected to the MQTT server. Then, we subscribe to one or more topics and define a callback function processMessage for processing the message. By calling the proc method, we can continue to receive and process messages from the MQTT server.

4. Equipment side
   In the remote energy monitoring and management system, the equipment side refers to energy usage equipment, such as sensors, smart meters, etc. The device needs to send energy usage data to the MQTT server in real time and receive control instructions from the server.

require("phpMQTT.php");

$server = "mqtt.example.com";
$port = 1883;
$client_id = "phpMQTT-publisher";
$topic = "energy/usage";

$mqtt = new phpMQTT($server, $port, $client_id);

if ($mqtt->connect(true, NULL, "username", "password")) {
    $usage_data = "100"; // 从能源使用设备中获取实时能源使用数据
    $mqtt->publish($topic, $usage_data, 0);
    $mqtt->close();
} else {
    echo "Failed to connect to MQTT server.";
}

In the above example, we created a phpMQTT object and connected to the MQTT server. We then use the publish method to send real-time energy usage data to the topic energy/usage.

5. Web Application
   Web application is the core of the remote energy monitoring and management system. It can receive energy usage data in real time by subscribing to topics on the MQTT server, and send control instructions by publishing topics.

require("phpMQTT.php");

$server = "mqtt.example.com";
$port = 1883;
$client_id = "phpMQTT-subscriber";
$topic = "energy/usage";

$mqtt = new phpMQTT($server, $port, $client_id);

if ($mqtt->connect(true, NULL, "username", "password")) {
    $mqtt->subscribe(array($topic => array("qos" => 0, "function" => "processMessage")), 0);
    while ($mqtt->proc()) {
        // 处理其他业务逻辑
    }
    $mqtt->close();
} else {
    echo "Failed to connect to MQTT server.";
}

function processMessage($topic, $message) {
    echo "Received message on topic: $topic
";
    echo "Message: $message
";
    // 在这里可以编写处理MQTT消息的代码逻辑
}

In the above example, we created a phpMQTT object and connected to the MQTT server. We then subscribe to the topic energy/usage and define a callback function processMessage for processing messages. By calling the proc method, we can continue to receive and process messages from the MQTT server.

Conclusion
Remote energy monitoring and management systems can be easily built using PHP and MQTT protocols. The lightweight and reliability of the MQTT protocol make it suitable for real-time communication between energy-using devices and web applications. Through real-time monitoring and remote control of energy usage, we can achieve the goals of energy conservation, emission reduction and sustainable development.

References:

1. Mosquitto - https://mosquitto.org/
2. phpMQTT - https://github.com/bluerhinos/phpMQTT

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