Real-time sensor data collection using PHP and MQTT

With the development of Internet of Things technology, more and more sensors are beginning to be used in various fields to provide us with more accurate data. However, how to efficiently collect and utilize this data has always been a concern in the industry. This article will introduce a real-time sensor data collection solution based on PHP and MQTT protocols.

1. Introduction to MQTT protocol

The MQTT protocol is a lightweight communication protocol based on the publish-subscribe model, which is suitable for small devices and low-bandwidth, unreliable networks. The MQTT protocol contains three main roles: publisher, subscriber and proxy server (broker). The publisher publishes data to a topic, and subscribers can subscribe to this topic to receive messages published by the publisher. The proxy server is responsible for forwarding and storing messages.

2. Implementation steps

1. Build an MQTT proxy server

Since the MQTT protocol requires a proxy server for message forwarding and storage, , we first need to build an MQTT proxy server. Common MQTT proxy servers include EMQ, Mosquitto, etc. This article takes EMQ as an example.

After installing EMQ, you need to perform some configuration, including opening the MQTT port, configuring the user name and password, etc. After the configuration is complete, you can connect to the proxy server through the MQTT client for testing.

2. Build a Web server

In order to collect sensor data in real time and process it, we need to build a Web server to receive and process the data. This article uses PHP language to build a Web server.

In PHP, we can use the Mosquitto PHP library to implement the functions of the MQTT client. First, you need to download and install the library and reference it into the PHP project.

3. Write PHP code

(1) Connect to the MQTT proxy server:

$mqtt = new MosquittoClient();
$mqtt->connect('localhost', 1883, 60);

(2) Subscribe to the topic:

$mqtt->subscribe('sensor/data', 0);

( 3) Process the message:

$mqtt->onMessage(function ($msg) {
    // 处理传感器数据
});

(4) Publish the message:

$mqtt->publish('sensor/data', 'hello, world!', 0);

(5) Start the client:

$mqtt->loopForever();

Through the above code, we can realize the core of the MQTT client Functions, including connecting to MQTT proxy server, subscribing to topics, processing messages and publishing messages, etc.

4. Connect to sensors and send data

In actual applications, we need to connect to actual sensors and send the data they collect to the MQTT proxy server. Here we take connecting a temperature sensor and sending the collected temperature data to the MQTT proxy server as an example.

Connect the temperature sensor to the Arduino board, and write a program through Arduino to collect temperature data and send it to the MQTT proxy server:

#include <Wire.h>
#include <Adafruit_MLX90614.h>
#include <PubSubClient.h>
#include <ESP8266WiFi.h>

Adafruit_MLX90614 mlx = Adafruit_MLX90614();
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);

void setup() {
  Serial.begin(115200);
  mlx.begin();
  WiFi.begin("ssid", "password");   //连接Wi-Fi
  while (WiFi.status() != WL_CONNECTED) {
      delay(1000);
  }
  mqttClient.setServer("localhost", 1883);   //连接MQTT服务器
}

void loop() {
  mqttClient.loop();   //连接MQTT服务器
  float temp = mlx.readObjectTempC();   //读取温度
  mqttClient.publish("sensor/data", String(temp).c_str());   //发送温度数据
  delay(5000);
}

Through the above program, we can connect the temperature sensor and collect it Temperature data, function to send it to MQTT proxy server.

5. Data processing and display

After receiving the data sent by the sensor, we can process it through PHP code, such as saving the temperature data to the database or performing Real-time display.

The specific method of processing and displaying sensor data using PHP code can be selected and designed according to actual needs.

3. Summary

This article mainly introduces a solution for real-time sensor data collection based on PHP and MQTT protocols. By connecting to the MQTT proxy server, using PHP code to implement the functions of the MQTT client, and connecting to the sensor and sending data, real-time data collection and processing of the sensor can be achieved. This solution can be widely used in various fields, such as smart homes, remote environmental monitoring, etc.

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