FTP is a standard protocol for transferring files between computers on the Internet. An FTP server runs FTP server software and listens on ports 20 and 21 to allow clients to connect and transfer files. FTP clients connect to FTP servers to upload and download files. There are two modes - active mode where the client initiates the data connection, and passive mode where the server initiates it to work better with firewalls. An FTP server is configured by installing vsftpd, enabling the service, editing configuration files, and adding users. FTP clients use commands like get, put, and mget/mput to download and upload files from/to the FTP server.

1. FTP SERVER

2. What is FTP?
● FTP stands for File Transfer Protocol.
● FTP is a standard Internet protocol for transmitting files between computers on the
Internet over TCP/IP connections.
● FTP is a client-server protocol.
● It relies on two communications channels between client and server:
1. A command channel for controlling the conversation
2. A data channel for transmitting file content.

3. Usage of FTP
● Uploading webpages to web servers or publishing on the Internet.
● Browsing and downloading files from public software sites.
● Transferring large files among two parties that are too large for email attachments.
● Distributing the latest revisions of programs by software developer.

4. What is FTP Server?
● An FTP server is a software program that is running on a server that uses
File Transfer Protocol (FTP) for exchanging files over the Internet.
Eg :- Vsftpd, Pure-FTPd, ProFTPD
- Vsftpd - fastest, most secure FTP server for Unix-like operatingsystem
- Pure-FTPd - simple, secure, highly-flexible FTP server
- ProFTPD - secure FTP server with a focus on configurability

5. What is FTP Client?
● A piece of software that you run on computer that will connect to an
FTP Server to download or upload files.
Eg :- FileZilla(Windows/Mac/Linux)
WinSCP(Windows)
FireFTP (Browser-based)
CyberDuck (Windows/Mac)

6. ● To transfer a file with FTP we need an FTP accounts.
● Remote computers can connect anonymously to ftp, if allowed, or with a
username and password in order to download files
● There are two additional types of FTP accounts.
1. Anonymous FTP
2. Regular FTP
FTP Accounts

7. Working of FTP Server
● FTP uses one connection for commands and the other for sending and receiving data.
● A port is a "logical connection point" for communicating using the Internet Protocol (IP).
● Standard port number used by FTP servers :
- The port used exclusively for sending commands is referred to as a command port.
21 - is used only for sending commands.
(Port 21 (unsecured) or 990 (secured))
● The port used for data transfers between the client and server is referred to as a data port.
20 - is used as data port.(The number of the data port will vary depending on the
"mode" of the connection.)

8. Types of FTP
● Active Mode
● Passive Mode

9. Active Mode
● In active mode,the FTP client (random port, X>1023) initiates the connection by
connecting to the server’s command port (Port 21).
● The client then opens a Listening data port and sends the command PORT to the
server.
● The server, using Port 20, will initiate the connection to the specified data port on the
FTP client.
● Problem with this is that the client simply tells the server which data port it is listening
to and the server is the one making the connection to the client.
● This causes the firewall to block this connection unless it was configured beforehand
to allow it.

11. Passive Mode
● The FTP client first establishes the connection by opening a port (random port,
X>1023) and connecting to Port 21 of the server.
● The client then opens another port X+1 and sends out the PASV command to notify
the server it is in passive mode.
● The server will respond by opening a port (predefined random port, Y>1023) and
acknowledges the client.
● Then the client initiates the connection from port X+1 to the server’s port Y for data
transferring.
● Because passive mode has the client initiating all connections, it works well across
firewalls

13. Configure FTP Server
1. # yum install vsftpd ftp -y
- vsftpd stand for Very Secure FTP Daemon.
- vsftpd is secure, fast and stable version of FTP.
- vsftpd efficiently handle large numbers of connection securely.
- ftp is FTP client, used to connect to an FTP server.

14. Configure FTP Server
2. # chkconfig vsftpd on
3. # service vsftpd start
4. # netstat -nltp
● Configuartion file : /etc/vsftpd/vsftpd.conf

15. Configure FTP Server
● Edit configuration file
# vim /etc/vsftpd/vsftpd.conf
change lines to
● permit any one to access FTP server with authentication
anonymous_enable=YES to anonymous_enable=NO

16. Configure FTP Server
● Uncomment the following line
local_enable=YES
- allow users in /etc/passwd to login
write_enable=YES
- allow users to write files. NO will permit only to read.
● Change the line
chroot_local_user=NO to chroot_local_user=YES
- This will permit local user as FTP account. If we add an user, it will be treated
as a FTP account as well. The local user home directory will act as FTP directory.

17. Configure FTP Server
● # service vsftpd restart
●
Connecting with ftp server
- Command line
# ftp 192.168.0.12
# ftp domain.com

18. Configure FTP Server
● Downloading files using FTP
ftp> lcd /home/user/yourdirectoryname
ftp> get filename
● To download several files we can use wildcards
ftp> mget *.txt
● Uploading Files with FTP
ftp> lcd /home/user/yourdirectoryname
ftp> put filename
● The file which we want to upload is not in the local directory
ftp> put /path/file
● To upload several files
ftp> mput *.txt