PHP and Modbus TCP: How to establish a stable communication connection

PHP and Modbus TCP: How to establish a stable communication connection

Abstract:
Modbus TCP is a commonly used communication protocol used for communication between devices in the field of industrial automation. This article will introduce how to use the PHP programming language to establish a stable communication connection with Modbus TCP devices and provide some code examples.

Introduction:
In the field of industrial automation, communication between devices is very important. Modbus TCP is a commonly used communication protocol that allows real-time data exchange between the master server and slave devices. PHP is a powerful programming language that can communicate with Modbus TCP devices to read and write data.

This article will use the PHP programming language to demonstrate how to establish a communication connection with a Modbus TCP device, and provide some simple code examples to help readers better understand and apply this technology.

Step 1: Install PHP Modbus Library
Before we begin, we need to install a PHP Modbus library for communicating with Modbus TCP devices. The library can be installed by executing the following command:

composer require phpmodbus/phpmodbus

Step 2: Establish Modbus TCP connection
First, we need to import the Modbus library in the PHP code, and then use the following code to establish the connection with the Modbus TCP device Connection:

<?php
require_once('vendor/autoload.php');

use PhpmodbusPhpmodbus;

$ip = '192.168.1.1';  // Modbus TCP设备的IP地址
$port = 502;  // Modbus TCP设备的端口号

$modbus = new Phpmodbus();
$modbus->connect($ip, $port);
?>

In the above code, we establish a connection to the Modbus TCP device by creating a Phpmodbus object. We need to provide the IP address and port number of the Modbus TCP device as parameters.

Step 3: Read the value of the Modbus register
Once the connection is established with the Modbus TCP device, we can use the following code to read the value of the Modbus register:

<?php
$response = $modbus->readMultipleRegisters(0, 10, 3);
if (!$response) {
    echo "读取Modbus寄存器失败！";
    exit;
}

$values = PhpmodbusUtilsModbus::parseMultipleRegisters($response);
print_r($values);
?>

Above In the code, we use the readMultipleRegisters() method to read the values ​​of 10 registers starting from 0. The data type of these registers is 3 (16-bit unsigned integer). The reading results are stored in the $response variable, and the parseMultipleRegisters() method needs to be used to parse the data.

Step 4: Write the value of the Modbus register
In addition to reading the value of the Modbus register, we can also use the following code to write the value of the Modbus register:

<?php
$data = array(1, 2, 3, 4, 5);  // 需要写入的值

$response = $modbus->writeMultipleRegisters(0, $data);
if (!$response) {
    echo "写入Modbus寄存器失败！";
    exit;
}

echo "Modbus寄存器写入成功！";
?>

In In the above code, we use the writeMultipleRegisters() method to write the values ​​in the $data array to registers starting from 0. If the write operation is successful, "Modbus register write successful!" will be output.

Conclusion:
By using the PHP programming language and the Modbus library, we can easily establish a communication connection with the Modbus TCP device and implement data reading and writing operations. This article gives some simple code examples to help readers better understand and apply these technologies. I hope this article can be helpful to readers in their work on device communication in the field of industrial automation.

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