First understand the principle of network

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One 、 Network division

1. LAN

Use some network devices to connect multiple hosts , These hosts can communicate with each other , That is to access the resources provided by each other , Such as ：

• html Webpage
• css file
• js file
• picture
• video
• music

Be careful ： If the LAN is not connected to the public network , Host in LAN , You can't access the resources of the public network

2. Wide area network

We all recognize the open network , All connected hosts can access

3. Network communication

Through the network , Get a resource on a host in the network

Two 、IP Address

Identify the network address of a host on the network

1. Format

Divided into four parts , In the middle "." interval , Each part 0~255(8 A bit , A byte )
This machine ip：127.0.0.1
For network communication ：
Such as ：A（ client ） visit B（ Server side ） A web page of

client ： Generally, it is the process used by users （ browser ）
Server side ： A process that provides resources （web The server ）
process ： A program that runs
Program ： Static executable file on hard disk

So we can't only find the host when communicating , To find out which process is on the host , How to find it ？ This is it Our process is identified by the port number

3、 ... and 、 Port number

Identification network communication , A process on a host
combination ip and port, You can know which host you want to get on the network , And resources in which process

Four 、 agreement

Network communication , The agreement that everyone should abide by 、 standard
Finally, it is embodied in the format of data packets
It is similar to doing programming problems on Niuke online , Input format ： For example, the first line is a number n, The second line is n A digital , Space interval

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