What Is a File Transfer?

File transfer refers to transferring a file or part of it from one computer system to another computer system.

Chinese name: file transfer
Foreign name: File transfer

By: A network connection
Features: The remote site copies files to the local host.
Applied discipline: Computer, communication

File transfer definition

File transfer is the transfer of a file or part of it from one computer system to another. Transfer a file or part of it from one computer system to another. It may transfer files to another computer for storage, or access files on remote computers, or transfer files to another computer to run (as a program) or process (as data), or transfer files to a printer. print. Because the file systems of computers on the network are often different, it is necessary to establish file transfer rules common to the entire network, called the File Transfer Protocol (FTP).

File transfer type

There are many types of file transfer ^[1]

For example, ftp, FTP is the English abbreviation for File Transfer Protocol, and the Chinese abbreviation is "Text Transfer Protocol". Used for bidirectional transmission of control files on the Internet. At the same time, it is also an application. Users can connect their PCs to all servers running the FTP protocol around the world and access a large number of programs and information on the server. The main function of FTP is to let users connect to a remote computer (these servers run FTP server programs) to see what files the remote computer has, and then copy the files from the remote computer to the local computer, or send the files of the local computer to The remote computer goes.

Remote login is one of the earliest Internet applications, and file transfer is the second developed application on the Internet. File transfer is implemented by the File Transfer Protocol (FTP). The basic idea is that the client logs in to the FTP server using a method similar to remote login, and then uses the commands of the file system of the machine to operate. In fact, many resources on the Internet are placed on FTP servers, such as some trial software, free software that is completely free to try, etc., we can use FTP to obtain them in large quantities. Therefore, FTP services and World Wide Web services both occupy important positions in the field of Internet applications.

File Transfer File Transfer Protocol

There are two file transfer protocol models in the network environment, namely a three-station model and a two-station model.

Three-station model file transmission involves three stations, one control station and two remote service stations. There is a control process on the control station, which is started by the user to control the file transfer. The two service stations are the source and destination stations for transmitting files, and both have service processes. In order to manage and perform file transfers, three connections need to be established between the control process and two remote service processes, and control connections are established between the control process and the two service processes to exchange control information, commands, and responses. A data connection needs to be established between the two service processes to transfer file data.

Two-station model file transmission involves only two stations, local host and remote host. The transmission and management of files is through the establishment and use of a single connection by both parties in the communication, that is, the control connection and the data connection are combined. On this single connection, both control information and data are transmitted. The remote host establishes a service process to provide access to local files. The local host has both control and service functions.

File transfer file transfer method

According to different purposes such as moving and storing files, printing files, and program input, there are three working modes for file transfer, namely information flow mode, compression mode, and information block mode.

The information flow method transmits the file as a byte stream. A file can be divided into logical records consisting of a series of logical units of bytes or machine words. At the end of a record or a file, there are "end" marks such as "end of record" or "end of file". The "end" flag consists of two bytes. The first byte is the "escape" byte and the second byte is the corresponding "end" byte. If the data bytes in the file are exactly the same as the "escaped" bytes, they are treated as character padding. In other words, the sender sends an "escaped" byte before the data byte, and the receiver removes one when it encounters two consecutive "escaped" bytes to achieve transparent data transmission.

The compression method also represents the file as a sequence of bytes for transmission, but compresses the bytes (such as blank characters) that repeatedly appear in order to improve the transmission efficiency. For this reason, this byte stream is composed of three components: regular data, compressed data, and control information. Each element is preceded by a byte indicating the relevant information. Use this method for printing files.

The information block method represents the file as a series of information blocks for transmission. Each block is preceded by a block header indicating the length of the information block.

Virtual file concept In computer systems, file formats and data representations are different, such as different character sets, encodings, and machine word lengths. In order to keep the semantics of the data unchanged when transferring files, corresponding conversions are required. In order to reduce the amount of conversion software, the concept of virtual files was introduced. Define a common virtual file structure and virtual file transfer system across the network. Develop a standard logical file structure and data representation. Each host must convert its file data into a standard form that can be transmitted on the network when transmitting files. The destination host then converts it to its local form when receiving. This solves the problem of incompatibility between different file management systems.

Common file transfer tools for file transfer

uploadify File transfer uploadify

uploadify is a free file upload plugin for jQuery that can easily upload a single or multiple files to a website. You can control the number of concurrently uploaded files and control the appearance through interface parameters and CSS. The web server needs to support flash and back-end development languages.

FancyUpload File transfer FancyUpload

Ajax file upload tool written in CSS and XHTML style, easy to install, server independent, driven by MooTools module, can be used on any modern browser.

Aurigma Upload Suite (Image Uploader)

This is a batch / file upload tool of unlimited size and format, which is a charge control. It supports cloud storage and client-side file processing, supports breakpoint resume transmission, and is stable and reliable. Starting from 8.0.8, Image Uploader changed its name to "Aurigma Upload Suite".

Multiple File Upload-JQuery

The Multiple File Upload Plug-in is a multiple file upload plug-in for the JQuery JavaScript library. It helps users select multiple files to upload at the same time, and can also identify some simple errors.

Mootool based Multiple file uploader

This is a lightweight multi-file upload tool based on MooTools, only 2.5K. There are some simple CSS, an HTML sample file and a readme.

AjaxFileUpload File transfer AjaxFileUpload

As the name suggests, this is an Ajax file upload tool, a hacked version of Ajaxupload created by yvind Saltvik. It simplifies the traversal of HTML documents, handles events, performs animations, and adds Ajax interactions to Web pages.

File upload progress bars with PHP

When uploading a file, a progress bar is generated through the file upload hooks of PHP 5.2.x.

Create An Ajax Style File Upload

This Ajax version of the file upload tool is easy to operate. When uploading a file using Iframe, the page is not refreshed, and a progress bar is displayed while uploading the file.

Styling inputs with css and dom

Style file input tool provides markup, CSS and JavaScript, designed to solve the problem that designers cannot express design ideas in detail, and supports IE 5.5+, Firefox 1.5+, Safari 2+.

jqUploader File transfer jqUploader

This is also a jQuery plugin with a progress bar and percentage on the interface. Can be directly defined in the menu using html code, such as the maximum file size. ^[2]