FTP for Linux basic services

1. What is FTP

FTP is referred to as File Transfer protocol and can be used for file sharing with remote computers. The protocol uses the TCP protocol, the FTP service port number is 21, the data port is 20. Typically, users who transfer files need to be authenticated before they can log on to the Web site to access remote server files. Most FTP servers often provide a guest's public account to allow users without a remote server to access the FTP server. The working process is as follows:

(1) The client makes a connection request to the server, while the client system opens a port greater than 1024 to wait for a server connection (such as 1028 port).

(2) The FTP server 21 port hears the request, then client 1028 will establish an FTP session connection between the server 21 port.

(3) When data transfer is required, the client opens a port greater than 1024 (for example, 1027 port) to connect to the server's 20 port and transfers data between the two ports until the two ports are automatically closed after the data transfer is complete.

(4) When the client and server are disconnected, previously dynamically allocated ports on the client are automatically freed.

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FTP for Linux basic services