What is the difference between FTP and sftp in linux?

Difference: 1. The link methods are different. FTP uses the "control connection" on TCP port 21 to establish a connection, while SFTP establishes a connection through the SSH protocol (TCP port 22); 2. SFTP uses encryption and decryption technology for transmission Data security is higher than FTP; 3. The transmission efficiency of SFTP is lower than FTP.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

The two most commonly used file transfer methods in actual Linux project development are ftp and sftp, but what are the characteristics of these two transmission methods? This article will discuss the differences between SFTP and FTP next.

1. FTP protocol

FTP is one of the protocols in the TCP/IP protocol group. The TP protocol consists of two parts:

• FTP server (used to store files)

• FTP client (users can use the FTP client to access files located on the FTP server through the FTP protocol Resources)

By default, the FTP protocol uses TCP ports 20 and 21. Port 21 is used to transmit control information, and whether to use 20 as the port to transmit data is related to the transmission mode used by FTP. If passive mode is used, the specific port to be used must be decided by negotiation between the server and the client. FTP transfer modes are divided into the following two types:

• Active mode (Port)

• Passive mode (Passive)

1. Active mode

The FTP client first establishes a connection with the TCP21 port of the FTP server and sends commands through this channel. When the end needs to receive data, it sends a PORT command on this channel. The PORT command contains the port used by the client to receive data. When transmitting data, the server connects to the client's designated port through its own TCP 20 port to send data.

2. Passive mode

#The establishment of a control channel is similar to the active mode, but the Pasv command is used after the connection is established. After receiving the Pasv command, the FTP server randomly opens a high-end port (the port number is greater than 1024) and notifies the client of the request to transmit data on this port. The client connects to this port of the FTP server, establishes the channel through a three-way handshake, and then the FTP server Data is transmitted through this port.

Note: Many firewalls are not allowed to accept externally initiated connections when they are set up, so many FTP servers located behind the firewall or on the intranet do not support PASV mode because the client cannot open FTP through the firewall. The high-end port of the server; many clients on the internal network cannot log in to the FTP server in PORT mode because the TCP 20 from the server cannot establish a new connection with the client on the internal network, causing it to fail to work.

SFTP protocol

SFTP is the abbreviation of SSH File Transfer Protocol, a secure file transfer protocol. SFTP has almost the same syntax and functionality as FTP. SFTP is part of SSH and is a secure way to transfer files to Blogger servers. In fact, the SSH software package already contains a secure file information transfer subsystem called SFTP. SFTP itself does not have a separate daemon. It must use the sshd daemon (the default port number is 22) to complete the corresponding connection and reply. Operation, so in a sense, SFTP is not like a server program, but more like a client program.

Main differences between SFTP and FTP

Linking method: FTP uses a control connection on TCP port 21 to establish a connection. However, SFTP is a secure connection established between the client and server through the SSH protocol (TCP port 22) to transfer files.

Security: SFTP uses encryption to transmit authentication information and transmitted data, so using SFTP is very secure compared to FTP.

Efficiency: SFTP is a transmission method that uses encryption and decryption technology, so the transmission efficiency is much lower than ordinary FTP.

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