How to use PHP to implement Modbus TCP data conversion and formatting

How to use PHP to realize data conversion and formatting of Modbus TCP

Introduction:
Modbus is a popular communication protocol commonly used in the field of industrial control. Modbus TCP is the application implementation of Modbus protocol on TCP/IP network. As a popular programming language, PHP can also be used to implement Modbus TCP data conversion and formatting. This article will introduce how to use PHP to write code to implement Modbus TCP data conversion and formatting operations.

1. Install the necessary PHP extensions and libraries
Before starting to write PHP code, we need to ensure that the necessary PHP extensions and libraries have been installed in the system. Specifically, we need to install the following extensions and libraries:

1. php_sockets extension: used to support TCP/IP communication.
2. php_modbus extension: used to support Modbus protocol. If you do not have this extension, you can download the corresponding library file from GitHub and install it.

2. Establish Modbus TCP connection
Before we begin, we need to establish a connection with the Modbus TCP server. Here is a simple PHP function for establishing a Modbus TCP connection:

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3. Sending and receiving Modbus TCP data packets
After establishing a connection with the Modbus TCP server, we can use PHP's socket function to send and receive Modbus TCP data packets. Here is an example function for sending a Modbus TCP read holding register request and receiving a response:

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In this example function, we use the pack function to format the request data of the Modbus TCP read holding register into a binary string and use the socket_write function Send request data to Modbus TCP server. Then, we use the socket_read function to receive the response data from the server. Please note that 1024 here is the size of the receive buffer, you can adjust it according to actual needs.

4. Parse Modbus TCP response data
After receiving the response from the Modbus TCP server, we need to parse the response data. The following is an example function for parsing response data from a Modbus TCP read holding register request:

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In this example function, we use the unpack function to parse the Modbus TCP response data into various parts, and store the value of the holding register in an array and return it.

Summary:
This article introduces how to use PHP to write code to implement Modbus TCP data conversion and formatting operations. We hope to be helpful to beginners by providing sample code for establishing a connection to a Modbus TCP server, sending and receiving Modbus TCP packets, and parsing Modbus TCP response data. Of course, actual applications may involve more functionality and complexity, but by understanding the contents of this article, you will be able to provide a basic Modbus TCP support for your application.

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