One 、FTP summary

FTP（File Transfer Protocal, Text transfer protocol ） Typical C/S Application layer protocol of architecture , The server software is required 、 The two parts of the client software jointly realize the file transfer function .FTP The connection between client and server is reliable , Connection oriented , It provides reliable guarantee for data transmission .
TCP agreement ：20,21 port

Two 、FTP Two modes of service

FTP It's a file transfer protocol , It supports two modes , One way is called Standard（ That is to say Active, Take the initiative ）, One is Passive（ That is to say PASV, passive ）.Standard The pattern is FTP The client sends PORT Order to FTP Server.Passive The pattern is FTP The client sends PASV Order to FTP Server

1.Standard Pattern

FTP The client first communicates with FTP Server Of TCP21 Port establish connection , Send commands through this channel , When the client needs to receive data, it will send it on this channel PORT command .PORT The command contains what port the client uses to receive data . When transmitting data , The server passes its own TCP20 Port send data .FTP Server A new connection must be established with the client to transmit data .

2.Passive Pattern

When establishing control channels and Standard Similar model , When the client sends through this channel PASV When ordered ,FTP Server Open a window located in 1024 and 5000 And notify the client of the request to transmit data on this port , then FTP Server Data will be transmitted through this port , This is the time FTP Server There is no longer a need to establish a new connection with the client

3、 ... and 、 Build and configure FTP service

3.1 preparation

3.1.1. Experimental environment

The server ：CentOS7 System ip：192.168.226.131
client ：Win10 System ip：192.168.226.160

3.1.2. Turn off firewall and core protection

Turn off firewall and core protection

systemctl stop firewalld       # Turn off firewall 
systemctl disable firewalld     # Turn on and turn off the firewall 
setenforce 0                   # Temporarily turn off the enhanced safety function 

3.1.3. install vsftpd Software

Linux In the system , yes vsftpd Provide ftp Service for

Turn on vsftp Service and view ports


Backup files , In case something goes wrong

3.2 Anonymous user access

3.2.1 Modify the configuration file

Edit the profile accessed by anonymous users


Give the maximum permission to access the directory

3.2.2 test

stay /var/ftp/pub Next create a file goodman

open win10 Command line , Enter into 192.168.226.131,pub Appear under directory goodman file

Download the file

The file will be downloaded locally

View file contents

Create a new file and upload it



Test success

3.3 Local user access

3.3.1 Modify the configuration file

Edit the configuration file accessed by local users




Give the maximum permission to access the directory

3.3.2 test

establish ngs.txt file

Use zhangsan User connection

download ngs.txt

establish zhangsan Upload files


/var/www/ngs/ There will be zhangsan.txt file

summary

FTP How it works
VSFTPD Two working modes of （ The difference between active and passive ）
FTP Port usage of
FTP Configuration and use of services
How to realize anonymous user login and local user login