File Transfer protocol (FTP)
FTP service enables an Internet user to move a file from one computer to another on the Internet . A file may contain any type of digital information. text document, artwork, image, movie, software, sound, etc . Downloading is the process of moving file a remote computer to one's own computer , and uploading is the process of moving a file from one's own computer to a remote computer.
In FTP service , a file transfer takes place in following mannner.
1. A user execute the ftp command on his/her local computer , specifying address of the remote computer as a parameter.
2. An FTP process running on user's computer (called FTP client process) establishes a connection with an FTP process running on remote computer (called FTP server process).
3. The system then asks the user to enter his/her login name and password on the remote computer to ensure that the user possesses permission to access the remote computer.
4. After successful login , the user downloads or uploads the desired file(s) by using get (for downloading) and put (for uploading) commands . The user can also list directories , or move between directories of the remote computer, before deciding which file(s) to transfer.
Notice that a user needs access rights for a remote computer to transfer files to/from it. with this restriction. it is almost impossible to provide access rights to the large number of users on the internet to a computer that contains sharable information. The concept of anonymous FTP site solves this problem . An anonymous FTP site is a computer allowing a user to log in with a username of anonymous and a password that is user's e-mail address.The user can then downlaod files that have been stored for sharing on this site(computer). Such sites are called publicly accessible sites because any user on the Internet can access them.
FTP service also provides restricted file access feacture . For this, a user needs a valid username and password for a computer to access files on that computer. For example, an organization may use this feature to let only authorized persons access the files on its server computer.
