(Starting with a diagram, the content relies on compilation)IntroductionRecently, while testing software for internal network penetration, I encountered many protocols that I do not specialize in and could not understand. I gathered relevant information to educate myself.Here’s a summary diagram Application Layer Protocols Application layer protocols are those that directly serve user applications in network … Read more
🎯 Core Functionality Send a string of data to a specified IP and port using the TCP protocol, including a timestamp and CRC check. 1. TCP Client Communication Establish a TCP connection with the specified server Continuously send structured data packets Support automatic reconnection mechanism Regularly send heartbeat packets to keep the connection alive 2. … Read more
Today, we will conduct a practical test to see how fast the communication speed is when implementing Modbus TCP communication with different brands of PLCs or boards. Testing Interface We used our self-developed communication library for testing. Different communication libraries may have slight differences, and the test results are for reference only and do not … Read more
1. Overview of PLC Socket TCP Client Communication: In socket TCP client communication, the client first calls a system function to create a TCP socket, then initiates a connection request to the server at a specified IP address and port. A reliable connection is established through a three-way handshake. The communication protocol can be customized … Read more
To understand the communication processes of Modbus TCP and Modbus RTU, we need to consider their frame structures, transmission mechanisms, and master-slave interaction logic. The former relies on the TCP/IP protocol stack for “reliable transmission,” while the latter transmits “binary data” directly over serial ports. The core differences lie in the “data encapsulation” and “link … Read more
In the context of the Internet of Things (IoT), the choice between TCP and UDP depends on the specific application requirements for reliability, latency, bandwidth, and device resources. Below is a detailed analysis of typical application scenarios, advantages and disadvantages, and selection recommendations for both protocols in IoT: 1. Application Scenarios of TCP in IoT … Read more
Click the blue text PLC Automation Exchange Follow us 1. Overview of Application ScenariosIn industrial automation projects, it is often necessary to achieve data communication between different devices. The Omron NX102-1200 PLC acts as a master station, reading floating point data from slave devices (such as sensors, instruments, other PLCs, etc.) via the MODBUS TCP … Read more
Understanding the Entire HTTP Request Process to the Backend 1. Client Initiates Request 1.1 User Action The user enters a URL in the browser or clicks a link, triggering an HTTP request. If it is a form submission or AJAX request, JavaScript constructs the request using <span>XMLHttpRequest</span> or <span>fetch</span> API. 1.2 Browser Constructs Request The … Read more
Introduction In unstable network environments, using the TCP transport protocol, MQTT may face challenges in ensuring reliable communication. To address this issue, MQTT introduces a QoS mechanism that provides various message interaction options to meet specific requirements for reliable message delivery in different scenarios. In this article, we will explore the QoS levels 0, 1, … Read more
Netizen Comments @TeaDelivery:Three-way handshake @BH1SMB:TCP: Starts boasting after three-way handshake, UDP: I sent it, whether you see it or not is none of my business… @Vine:I still prefer “What are you looking at?” “What are you gonna do about it?” “Come here, let’s chat” @RAVI-Li:No matter if you listen or not, I’m just a UDP … Read more