How to implement industrial equipment communication through PHP and Modbus protocol

How to realize industrial equipment communication through PHP and Modbus protocol

Abstract: As industrial equipment becomes more intelligent and automated, industrial equipment communication protocols become more and more important. This article will introduce how to implement communication with industrial equipment through PHP language and Modbus protocol, and give corresponding code examples.

1. What is Modbus protocol
Modbus protocol is a protocol used for industrial equipment communication. It is often used in the field of industrial automation. The Modbus protocol defines a set of communication rules that can realize communication and data exchange between devices from different manufacturers.

There are multiple variants of the Modbus protocol, the most common ones are Modbus TCP (based on TCP/IP protocol) and Modbus RTU (based on serial communication). Among them, Modbus TCP is a communication protocol based on Ethernet, which can realize real-time communication between devices; Modbus RTU uses serial port communication, which is more common in practical applications.

2. Principle of communication between PHP and Modbus protocol
PHP is a commonly used server-side scripting language that can be used to process network requests and generate dynamic web pages. The basic principles of industrial equipment communication through PHP language and Modbus protocol are as follows:

1. Create TCP connection or serial port connection: According to the specific application situation, establish a communication connection with industrial equipment. For Modbus TCP communication, you can use PHP's socket function library to create a TCP connection; for Modbus RTU communication, you can use PHP's serial port function library to establish a serial port connection.
2. Construct Modbus request data packet: Construct the Modbus request data packet to be sent according to the format specified by the Modbus protocol. Usually includes information such as device address, function code, register address, etc.
3. Send Modbus request packet and receive response: Send the constructed Modbus request packet through TCP or serial port and wait for the response from the industrial device. Obtain the required data based on the data packet response from the device.
4. Processing device response data: According to the format specified by the Modbus protocol, the device response data is parsed and processed to extract the required data.
5. Disconnect: After the communication is completed, close the TCP connection or serial port connection.

3. PHP implementation of Modbus TCP communication example

The following is a simple PHP code example to demonstrate how to use PHP language to communicate with Modbus TCP:

<?php
$serverIP = '192.168.0.1';  // Modbus TCP服务器IP
$serverPort = 502;  // Modbus TCP服务器端口

// 创建TCP连接
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
$result = socket_connect($socket, $serverIP, $serverPort);
if ($result === false) {
    die("无法连接到Modbus TCP服务器");
}

// 构建Modbus请求数据包（读取寄存器）
$request = pack('nnnn', 0x0001, 0x0004, 0x0000, 0x0008);

// 发送请求数据包
socket_write($socket, $request);

// 接收响应数据包
$response = socket_read($socket, 1024);

// 处理响应数据包
$data = unpack('n*', $response);
print_r($data);

// 关闭TCP连接
socket_close($socket);
?>

Above The sample code creates a TCP connection via PHP and sends a request to read a register (start address 0, length 8) to the Modbus TCP server. Then receive and process the server's response, and parse the response data into an array and output it.

4. Summary
This article introduces how to use PHP language and Modbus protocol to achieve communication with industrial equipment. By constructing a Modbus request packet and using the corresponding PHP functions to send and receive, communication with industrial equipment compatible with the Modbus protocol can be achieved. This article also provides sample code for PHP and Modbus TCP communication to help readers better understand and apply it. I hope this article will be helpful to readers in their study and research on industrial equipment communication.

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