One 、FTP（File  Transfer  potocol） File transfer association

FTP Is a 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 the client and the server is reliable , Connection oriented , It provides reliable guarantee for data transmission .tcp Agreement for 20,21 port .

21 port ： Used to establish a connection , Transmit instructions

20 port ： For data transfer

FTP It's a file transfer protocol , It supports two modes , One way is called Standard( That is to say Active, Active way ), One is Passive( That is to say PASV Passive way )：

Standard Pattern （ Active mode ）
FTP The client first communicates with FTP Server Of TCP
21 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 , Server side through their own TCP 20 Port send data . FTP server A new connection must be established with the client to transmit data .

Passive Pattern （ Passive mode ）
When establishing control channels and standard Similar model , When the client sends through this channel PASV When ordered ,FTPserver 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

  Two 、 stay centos7 On the configuration ftp service

1、 install ftp

yum install -y vsftpd

2、 Turn off firewall

systemctl stop firewalld
setenforce 0

 3、 Set up service startup

systemctl enable vsftpd
# Boot up 
systemctl start vsftpd
# Turn on vsftpd
systemctl status vsftpd
# see vsftpd The state of 

  4、 modify ftp The configuration file ( Anonymous user access )

vim  /etc/vsftpd/vsftpd.conf

 5、ftp Folder location of the service

/var/ftp/pub/

3、 ... and 、 Test anonymous user login ftp

stay /var/ftp/pub/ Next create a txt text file

stay windows On this PC , Input ftp The address of the server （ Deploy ftp Of the server ip）

The format is as follows

success  

   Four 、 Account password login ftp

Get into /etc/vsftpd/vsftpd.conf Set the configuration file

 12 anonymous_enable=NO
# Turn off anonymity 
 23 local_umask=033
# Set to divide root No permission to use outdoors 
 33 #anon_mkdir_write_enable=YES
 34 #anon_other_write_enable=YES
# Comment out anonymous user settings 

125 listen_ipv6=YES
126 local_root=/data/B/ftp    # Specify the directory to which the user logs in , This directory is the root directory where the login user logs in 
127 pam_service_name=vsftpd
128 userlist_enable=YES
129 tcp_wrappers=YES
130 allow_writeable_chroot=YES

Get into /etc/vsftpd/chroot_list Add the user name with restricted login

vim /etc/vsftpd/chroot_list

paul

test , Using the user paul To log in, you need to enter a password