Introduction to socke programming

This article is a reading note , Not in-depth study , If not required , Please forgive me .

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1. background

It took a long time （ About a week , I'm so rubbish ） After reading an English article :Bee’j Guide to Network Programming¹. There's another book ：《TCP/IP Sockets in C - Practical Guide for Programmers》 And a copy of PPT：《Introduction to Sockets Programming in C using TCP/IP》, No, it's just that I haven't finished reading the two later , It's older too , After all, I want to use IPv6, Instead of IPv4.【 to update , The book we are talking about now has a second edition , Joined the IPv6 The content of , Chinese translation ：TCP/IP Sockets Programming (C Language implementation )】
In fact, I have studied online books in my undergraduate course , The most important thing about the network is not ISO/OSI, It is TCP/IP, After all, according to the teacher ,ISO/OSI It was a group of people who came up with it when they were drunk , They correspond to each other 7 A dwarf ², Finally, it is later than the factual standard TCP/IP, Even according to ISO/OSI Here we are , And failed , Because it's so complicated .

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2. Basics

stay TCP/IP in , Layers of abstract encapsulation , The lower layer is transparent to the upper layer , The upper layer is the data part of the lower message format , The header is some control information .

Socket Programming lies below the application layer 、 Above transport layer . Divided into Stream Socket and Datagram Socket, In fact, they correspond to the two protocols of the transport layer ,TCP and UDP. But here comes the problem , If it is DCTCP How did this kind of advanced gadget come about ？ Let's discuss it later .
also C/S framework , In fact, there are two architectures ：P2P as well as C/S Each has its own advantages and disadvantages , However, this article only covers C/S,B/S yes C/S A special case of ,P2P I haven't studied it yet .C/S The architecture is similar to the following figure ：

by the way , The author is in *nix The platform does ,Windows Just mentioned the following ：Winsock.h

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3. technological process

Socket The programming process is actually not complicated .

So the whole process comes out , Is to create Socket, Then bind (bind), Actually connect() Can replace bind(), But the difference is ,bind() Binding port , and connect Don't care which port to use , Of course, for the parameters passed ,connect() Will help programmers find an unbound port to bind . The server listens for connection requests to this port , The rest is to send 、 I got the data , Note here Stream Socket（ Use TCP Connect ） and Datagram Socket（ Use UDP There is no connection ） The functions used for sending and receiving are different . Finally, don't forget to close Socket.

In fact, the rest is mainly to see what parameters are required for each function , Just how to use it , In the penultimate chapter of the article man pages, Or refer to another blog of mine Socket Programming based API, No post here . Theoretically, the following should be given Client/Server Of the program , But I don't think it's necessary . Follow the blog link I gave ¹ There were many in the past , No more .
However, you can list the most used header files .

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h> 
 	
#include <unistd.h>
#include <sys/socket.h> 
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

If you have the time , I'll add it when I'm more proficient .³

4. Reference resources

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1. Beej’s Guide to Network Programming︎︎

2. OSI How many people have the model fooled ?︎

3. Linux Of SOCKET Programming details ︎