Software development framework
. 1 C / S architecture
c client
s server
2 B / S architecture
b browser
s server
c / s architecture like on our software on the phone now, most of c / s architecture
There are also some already b / s architecture, such as micro-letters, in small programs, third-party payment of treasure features.
What is the server, and the client
The server is available 24 hours uninterrupted service
The client is, any time you can go to find the server, for service
History of network programming
Technological developments are often a source of military
Network communication conditions have
A physical transmission medium (telephone lines, cable, network card)
2 a common set of protocols (OSI protocol, for example, two different classes of people, you want to exchange, you must learn the same language, so will define a set of protocols)
OSI protocol (The seven formulas; correspondence table will pass network number thereof)
The OSI 7 layers protocol
Application layer
Presentation layer
Session Layer
Transport Layer
Network layer
data link layer
Physical connection layer
We feel developer layer 5 is enough, and then divided into five layers on the right
Application layer
Transport Layer
data link layer
Physical connection layer
What is the physical connection layer
Based on the electric signal, connect two 229
What is the data link layer (Ethernet protocol)
A grouping predetermined electrical signal, the binary grouping
2 provides, each computer connected to the Internet connection have to have a compulsory card
Each piece of card engraved with the world's unique hexadecimal number of a 12
The top six vendors are numbered
After six is the number of water
This is our computer's mac address
A flowchart of the switch
Switches, Ethernet-based communications
Note that the switch is not across the LAN communication, if there are many computers have access to a computer, there will be a broadcast storm
Broadcast; switch, to each of the requesting computers
Unicast, requesting the computer to the switch
If we want to we need to communicate across the LAN router
Routers work flow chart
A LAN, LAN server in order to access another,
You must use a router
互联网是由多个局域网连接而成的
什么是网络层
IP协议
规定一台接入互联网的计算机，必须有一个ip地址
ip地址的特点，点分十进制
ip最小地址 0.0.0.0
ip最大地址 255.255.255.255
ip地址现在有两个版本 ipv4 ipv6
ip地址是动态分配的
什么是传输层
TCP/UDP都是基于端口的工作协议
计算机与计算机之间实际上是通过计算机上的应用软程序来通信的
端口用来标识计算机上的应用程序
端口号的范围0-65535
注意0-1024是操作系统默认使用的端口号
我们应该使用8000之后的端口号
常用软件的端口号
mysql 3306
redis 6379
django 8000
flask 5000
什么是应用层
http协议
ftp协议
TCP协议
流式协议，可靠协议
基于tcp通信，必须建立双向通道
tcp的三次握手，四次挥手
tcp协议的稳定性在于，传输数据时候，是有反馈的
如果服务器给客户端传输数据，客户端没有给服务器返回反馈
服务端就会隔一段时间，再给客户端发数据
如果，客户端一直没有反馈数据
服务端就会关闭通道
图解；
三次握手
四次挥手
