Search on WeChat Technical Training Introduction Today, let’s talk about Modbus. First, let’s look at the main content for today: 01 Terminology Interpretation 02 Background 03 Protocol Principles 04 Transmission Methods 05 Differences Between Modbus RTU and Modbus ASCII 06 Modbus TCP and Its Considerations 07 Function Code Functions 08 Modbus Protocol Security Analysis 01 … Read more
/ Network Layered Structure / Consider the simplest case: communication between two hosts. At this point, only a single network cable is needed to connect the two, specifying their hardware interfaces, such as both using USB, 10v voltage, and 2.4GHz frequency. This layer is the physical layer, and these specifications are the physical layer protocol. … Read more
This article is a translation of “Let’s code a TCP/IP stack, 1: Ethernet & ARP”. The translation process is also a learning experience for myself. Writing your own TCP/IP stack may seem like a daunting task. In fact, TCP has accumulated many specifications over its more than thirty years of life. However, the core specifications … Read more
Fact One: File Descriptor Limits Friends who write network server programs in Linux surely know that each TCP connection occupies a file descriptor. Once this file descriptor is exhausted, a new connection attempt will return the error “Socket/File: Can’t open so many files”. At this point, you need to understand the operating system’s limit on … Read more
Click the blue text Follow us In daily life, when shopping online or mailing an item, we need to fill in both parties’ addresses, contact information, whether insurance is needed, and other details. Additionally, the courier company may have other regulations to be added to the purchase and mailing details. The purpose of this is … Read more
Source: https://juejin.cn/user/3931509313252552/postse In communication and IT work, networking is essential, and the most important protocol in the network is TCP. Whether in actual work or in written exams and interviews, you can’t escape TCP. I have read documents related to TCP in the RFC, examined the source code related to TCP in Linux, and looked … Read more
In network technology, a port generally has two meanings: first, it refers to the physical interface (hardware) between computers and other devices. For example, interfaces like RJ-45 ports and SC ports used to connect other network devices such as switches and routers. Second, it refers to the logical virtual ports (software), which typically refer to … Read more
Fundamentals of Networking 1、OSI（Open System Interconnection）Open System Interconnection Model Seven-layer model: Layer 1: Physical Layer : Transmission of raw bit streams over mechanical, electronic, and timing interfaces communication channels Layer 2: Data Link Layer: Physical addressing, while transforming the raw bit stream into logical transmission lines Layer 3: Network Layer: Controls the operation of subnets, … Read more
4 Network Layer IP The transmission of packets mainly goes through Application Layer, Transport Layer, Network Layer, and Link Layer. Following the explanation of the application layer HTTP and Transport Layer TCP, the application layer data is encapsulated by the transport layer and then needs to be encapsulated by the network layer. The core task … Read more
1. Introduction to TCP/IP The IP protocol is the network layer, the TCP protocol is the transport layer, the HTTP protocol is the application layer, and socket is the code encapsulation and application of the TCP/IP protocol. TCP/IP mainly addresses how data is transmitted over the network, while HTTP mainly deals with how to package … Read more