protocolftp是什么意思（What does FTP mean）

ftp是什么意思What does FTP mean

What does "FTP" mean?

Best answer: FTP is a software for uploading and downloading.I don't use much. I used to use my FTP to get things from mycomputer to the free space on the Internet, and it can also beused to download files, as long as there is an address.The FTP is defined as follows:

FTP (File Transfer Protocal) is a bidirectional transportprotocol for control files on Internet. At the same time, itis also an application. Users can connect their PC machines withall the servers running FTP protocols around the world, andaccess a large number of programs and information on the server.The general steps for transmitting files are as follows:1 log on to the Internet on your local computer,

2 search has a file sharing host or personal computer (usuallyposted on a special FTP server website, with the name, password,and path of access to the host or personal computer)

3 when you establish a connection with the remote host or thepersonal computer of the other party, login to the host orpersonal computer of the host with the username and passwordprovided by the other party

4 in the remote host or other personal computer after thesuccessful landing, you can upload it you want to share with

others stuff or download other people authorized to share stuff(here refers to the stuff on the computer to see on the screenand stuff)

5 after the completion of the work, turn off the FTP downloadsoftware, cut off the connection

In order to achieve file transfer, users also need to run adedicated file transfer program, such as the Internet Expresshas this function, there are many other special FTPtransmission software, each has its own characteristicsWhat is FTP?FTP is one of the protocols in the TCP/IP protocolgroup. It is the abbreviationof English File Transfer Protocol.This protocol is based on the Internet file transfer, itconsists of a series of specification documents. The goal isto improve the sharing of documents, provide non direct accessto the remote computer, the storage medium transparent to theuser and the reliable and efficient transmission of data. Inshort, FTP is the copy between two computers, copying f iles fromremote computers to their own computers, called download f iles.If you copy a file from your computer to a remote computer, itis called "Upload" file. In the TCP/IP protocol, the FTPstandard command TCP port number is 21, and the Port mode dataport is 20. The task of the FTP protocol is to transfer filesfrom one computer to another computer, which is independent ofthe location, connection mode, and even the use of the sameoperating system of the two computers. Suppose that twocomputers communicate through the FTP protocol and can accessInternet, and you can use the FTP command to transfer files.There are some subtle differences in the use of each operating

system, but the basic command structure of each protocol is thes ame.

There are two ways to transmit FTP: ASCII transmission mode andbinary data transmission mode.

Transmission mode: 1.ASCII assumes that the user is a copy ofthe file contains a simple ASCII text, if you are running ona remote machine is UNIX, when the file transfer FTP willusually automatically adjust the contents of the file intoanother file in order to explain that the computer stored ina text file format.

But it is often the case, the user is not the transmission filecontains the text files, they may be procedures, databases,word processing files or compressed files (although most wordprocessing documents are included in the text, which alsocontains the instructions page size, font information of nonprinting characters) . Before copying any non text files, usethe binary command to tell the FTP verbatim copy, not to processthese files, andthis is thebinarytransmissionto be describedbelow.

2. binary transmission mode: in the binary transmission, savethe order of the file, so that the original and copy is bit bybit one-to-one correspondence. Even if the file on thedestinationmachine contains a bit sequence is meaningless. Forexample, Macintosh sends executable files to theWindows systemin binary form, on the other party system,

This file cannot be executed.

If you transfer binary files in ASCII mode, even if you don'tneed it, you' ll still translate it. This slows the transmissionslightly, and also damages the data, making the file useless.On most computers, the ASCII pattern generally assumes that thefirst significant bit of each character is meaningless becausethe ASCII character combination does not use it. If you transferbinary files, all bits are important If you know that the twomachines are the same, the binary way is valid for both textand data files.

5. , FTP' s way of working

FTP supports two modes, one way is called Standard (that is,PORT mode, active mode) , and the other is Passive (that is, PASV,passive mode) . The client of FTP mode sends the PORT commandto the FTP server Standard. Passive mode FTP client sends PASVcommand to FTP Server.

Here is a brief introduction to the working principle of thetwo methods:

In Port mode, the FTP client first connects with the TCP 21 portof the FTP server, and sends commands through the channel. Theclient sends the PORT command on the channel when it receivesthe data. The PORT command contains what port the clientreceives data. When transmitting data, the server sends datathrough its own TCP 20 port to the specified port of the client.FTP server must establish a new connection with the client totransfer data.

The Passive pattern is similar to the Standard pattern insetting up control channels, but it is not the Port command butthe Pasv command that is sent after the connection isestablished. The FTP server receives a Pasv command, randomlyopened a high-end port (port number greater than 1024) andnotify the client for transmitting data in the client port, thisport and then connect to the FTP server, the FTP server willthrough this port for data transmission, this time FTP serverno longer need to establish a connection between the new andclient.

A lot of firewall in the set time are not allowed to acceptexternal initiated connections, so many located behind afirewall or intranet FTP server does not support PASV mode,because the client can not pass through the firewall to openthe FTP server and the client port high-end; not many networkmodels with PORT login FTP server for the establishment of anew the connection from the server TCP 20 and internal networkclient, resulting in no work.