Introduction to FTP File Transfer Protocol

During the download process, we will use thunder and BT software for download. Before that, we also introduced the BT protocol, that is, the file transfer protocol. Here we will introduce an FTP file transfer protocol. The FTP File Transfer Protocol is short for File Transfer Protocol ". It is used for controlling two-way transmission of files over the Internet. It is also an Application ). You can use it to connect your PC to all servers running the FTP protocol around the world to access a large amount of programs and information on the server. The main function of FTP is to allow users to connect to a remote computer and run FTP server programs on these computers) to check what files are available on the remote computer, then copy the files from the remote computer to the local computer, or send the files from the local computer to the remote computer.

Working principle of FTP File Transfer Protocol

Taking file downloading as an example, when you start FTP to copy files from a remote computer, two programs are actually started: an FTP client program on a local machine, which initiates a file copy request to the FTP server. The other is to start an FTP server program on a remote computer, which sends your specified file to your computer in response to your request. FTP adopts the "Client/Server" mode. The client must install the FTP client program on its local computer. The FTP client program has two types: character interface and graphical interface. The FTP commands on the Character interface are complex and numerous. Graphic Interface FTP client program, operations must be simple and convenient.

Simply put, the FTP server is the server that supports the FTP protocol. The following describes what is the FTP file transfer protocol. File Transfer Protocol)

In general, the primary purpose of user networking is to achieve information sharing, and file transmission is one of the most important aspects of information sharing. It is not easy to transmit files on the Internet at an early stage. We know that the Internet is a very complex computer environment with PCs, workstations, MAC, and mainframes, there are tens of millions of computers connected to the Internet, and these computers may run different operating systems and Unix servers, there are also PCs running Dos, Windows, and MacOS running. A Unified File Transfer Protocol is required for file communication between various operating systems. This is called FTP. There are different FTP applications based on different operating systems, and all these applications comply with the same protocol, so that users can transmit their files to others, you can also obtain files from other user environments.

Like most Internet services, FTP is also a client/server system. You can use a client program that supports the FTP protocol to connect to the FTP server program on a remote host. The user sends commands to the server program through the client program. The server program executes the commands issued by the user and returns the execution results to the client. For example, if a user sends a command that requires the server to send a copy of a file to the user, the server will respond to the command and send the specified file to the user's machine. The client receives the file and stores it in the user directory.

When using the FTP File Transfer Protocol, users often encounter two concepts: "Download" Download) and "Upload" Upload ). "Download" means to copy files from the remote host to your computer. "Upload" means to copy files from your computer to the remote host. In the Internet language, you can use a client program to upload and download files to a remote host.

When using FTP, you must first log on and obtain the relevant permissions on the remote host before downloading or uploading files. That is to say, if you want to transfer files to the same computer, you must have the appropriate authorization for that computer. In other words, files cannot be transmitted unless you have a user ID and password. This situation violates the openness of the Internet. It is impossible for every user to have an account on every host because the FTP host on the Internet is tens of millions. Anonymous FTP is generated to solve this problem.

Anonymous FTP is a mechanism in which users can connect to a remote host and download files from it without having to become their registered users. The system administrator creates a special user id named anonymous, which can be used anywhere on the Internet.

Using an FTP program to connect to an anonymous FTP host is similar to connecting to a common FTP host. However, you must enter anonymous when requesting the user ID. the user ID password can be any string. Traditionally, you can use your own email address as a password so that the system maintenance program can record who is accessing these files.

It is worth noting that the anonymous FTP File Transfer Protocol is not applicable to all Internet hosts. It is only applicable to hosts that provide this service.

When the remote host provides anonymous FTP service, some directories are specified to be open to the public and anonymous access is allowed. The remaining directories in the system are hidden. As a security measure, most anonymous FTP hosts allow users to download files from them, rather than uploading files to them. That is to say, you can copy all files on the anonymous FTP host to your machine, but you cannot copy any file on your machine to the anonymous FTP host. Even if some anonymous FTP hosts allow users to upload files, they can only upload files to a specified upload directory. Then, the system administrator checks these files and moves them to another public download directory for other users to download. In this way, users on the remote host are protected, this prevents someone from uploading problematic files, such as files with viruses.

As an Internet user, you can copy files between any two Internet hosts through FTP. However, most people only have one Internet account. The FTP File Transfer Protocol is mainly used to download public files, such as shared software and technical support files of various companies. There are thousands of anonymous FTP hosts on the Internet, which store countless files for free copying. In fact, almost 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 gives users the opportunity to access the world's largest information library, which has been growing over time and will never be closed, involving almost all topics. And it's free.

Anonymous FTP is a common method for publishing software on the Internet. The reason why the Internet continues today is that people use programs that provide standard services through standard protocols. Many programs like this are published through anonymous FTP and can be accessed by anyone.

There are a large number of anonymous FTP File Transfer Protocol hosts and more files in the Internet. So how can we know which one of the specific files is located in the directory of the anonymous FTP host? This is exactly what the Archie server needs to do. Archie will automatically search in the FTP host to construct a database containing all the file directory information, so that you can directly find the location information of the desired file.