What is FTP (File Transfer Protocol)?

File Transfer Protocol
FTP (file Transfer Protocol), which is the short name of the document transfer Protocol. Used for two-way transmission of control files on the Internet. At the same time, it is also an application (application). It allows users to connect their PC to all servers running the FTP protocol around the world, accessing a large number of programs and information on the server.
[edit this paragraph] The role of FTP
As the name suggests: The primary role of FTP is to have users connect to a remote computer (which runs an FTP server program) to see what files are on the remote computer, then copy the files from the remote computer to the local computer, or send the local computer's files to the remote computer.
[edit this paragraph] How FTP Works
Take the file as an example, when you start FTP copy files from a remote computer, you actually launch two programs: an FTP client on a local machine: it asks the FTP server for a copy of the file. The other is the FTP server program that launches on the remote computer, and it responds to your request to transfer the files you specified to your computer. FTP uses a "client/server" approach, where the client installs FTP clients on its own local computer. The FTP client has two types: the character interface and the graphical interface. The ftp command of the character interface is complex and numerous. Graphical interface of the FTP client program, the operation to be concise and convenient more.
Simply put, the FTP server is the FTP server, the following describes what is the FTP protocol. (File Transfer Protocol)
Generally speaking, the primary purpose of user networking is to realize information sharing, and file transfer is one of the most important content of information sharing. Early implementation of the Internet on the transfer of files is not an easy thing, we know that the Internet is a very complex computer environment, there are PCs, workstations, Mac, a mainframe, according to statistics connected to the Internet computer has tens of millions of stations, And these computers may run different operating systems, there are servers running UNIX, there are running DOS, Windows PC and Mac running MacOS and so on, and the various operating systems between the file Exchange problem, need to establish a unified file transfer protocol, which is called FTP. There are different FTP applications based on different operating systems, and all of these applications follow the same protocol, so that users can transfer their files to others or get files from other user environments.
Like most Internet services, FTP is also a client/server system. The user connects to the FTP server program on the remote host through a client program that supports the FTP protocol. The user sends commands to the server program through the client program, the server executes the commands issued by the user, and returns the results of the execution to the client. For example, a user sends a command asking the server to send a copy of a file to the user, and the server responds to the command, sending the specified file to the user's machine. The client program receives the file on behalf of the user and stores it in the user directory.
In the use of FTP, users often encounter two concepts: "Download" (Download) and "Upload" (Upload). A "Download" file is a copy of a file from a remote host to its own computer; the "upload" file is a copy of the file from your computer to a remote host. In the Internet language, users can upload (download) files to (from) a remote host through a client program.
When using FTP, you must first log in and obtain the appropriate permissions on the remote host before you can upload or download the file. That is, if you want to transfer files to the same computer, you must have the appropriate authorization for which computer. In other words, the file cannot be transferred unless there is a user ID and password. This situation violates the openness of the Internet, the FTP host on the internet is more than tens of millions, it is impossible to require each user to have an account on each host. Anonymous FTP was created to solve this problem.
Anonymous FTP is a mechanism by which a user can connect to a remote host and download files from it without becoming a registered user. The system administrator has established a special user ID, named Anonymous, that can be used anywhere on the Internet by anyone.
The FTP program connects anonymous FTP hosts in much the same way as a normal FTP host, except that anonymous must be entered when a user ID is required, and the password for that userid can be any string. In practice, use your own e-mail address as a password, so that the system maintenance program can record who is accessing these files.
It is important to note that anonymous FTP does not apply to all Internet hosts, it only applies to those hosts that provide the service.
When the remote host provides an anonymous FTP service, certain directories are specified to be open to the public, allowing anonymous access. The remaining directories in the system are in a stealth state. As a security measure, most anonymous FTP hosts allow users to download files from them without allowing users to upload files to them, which means that the user can copy all the files on the anonymous FTP host to their own machine, but cannot copy any of the files on their machine to an anonymous FTP host. Even if some anonymous FTP hosts do allow users to upload files, users can only upload files to a specified upload directory. Then, the system administrator will check these files, he will move these files to another public download directory for other users to download, in this way, the remote host users are protected from uploading the problematic files, such as files with viruses.
As an Internet user, you can copy files between any two Internet hosts via FTP. However, most people actually have only one Internet account, and FTP is used primarily to download public files, such as shareware, company technical support files, and so on. There are thousands of anonymous FTP hosts on the Internet that hold countless files for free copies. Virtually all types of information, all types of computer programs, can be found on the Internet. This is one of the important reasons why the Internet attracts us.
Anonymous FTP users have the opportunity to access the world's largest information base, which has accumulated over time and is growing, never closed, and involves almost all topics. And, it's all for free.
Anonymous FTP is a common method of publishing software on Internet. The internet continues today because people use programs that provide standard services through standard protocols. Many of these programs, like this one, are published by anonymous FTP and can be accessed by anyone.
With a huge number of anonymous FTP hosts and more files in the Internet, how exactly do you know which directory is on the anonymous FTP host for a particular file? This is exactly what the Archie server is doing. Archie will automatically search the FTP host, construct a database containing all the file directory information, so that you can directly find the location information of the required files.

What is FTP (File Transfer Protocol)?