FTP  -  File Transfer Protocol

The process by which files are transferred to the web server is called "FTP" (File Transfer Protocol). You have unlimited access via FTP 24 hours a day. As such, you can create and maintain your web pages on your own computer and upload files to your web site at your leisure and you may set up as many FTP user accounts as you like in your Site Manager.

Overview

FTP is commonly run on two ports, 20 and 21. Port 20 is a data stream which transfers the data between the client and the server. Port 21 is the control stream and is the port where commands are passed to the ftp server. While data is being transferred via the data stream, the control stream sits idle. This can cause problems with large data transfers through firewalls which time out sessions after lengthy periods of idleness. While the file may well be successfully transferred, the control session can be disconnected by the firewall, causing an error to be generated.   The objectives of FTP, as outlined by its RFC, are: To promote sharing of files (computer programs and/or data). To encourage indirect or implicit use of remote computers. To shield a user from variations in file storage systems among different hosts. To transfer data reliably and efficiently.   Disadvantages are: Passwords and file contents are sent in clear text, which can be intercepted by eavesdroppers. Multiple TCP/IP connections are used, one for the control connection, and one for each download, upload, or directory listing. Firewall software needs additional logic to account for these connections. It is hard to filter active mode FTP traffic on the client side by using a firewall, since the client must open an arbitrary port in order to receive the connection. This problem is largely resolved by using passive mode FTP. It is possible to abuse the protocol's built-in proxy features to tell a server to send data to an arbitrary port of a third computer.   FTP, though usable directly by a user at a terminal, is designed mainly for use by FTP client programs. Many sites that run FTP servers enable so-called "anonymous ftp". Under this arrangement, users do not need an account on the server. By default, the account name for the anonymous access is 'anonymous'. This account does not need a password. Although users are commonly asked to send their email addresses as their passwords for authentication, usually there is trivial or no verification, depending on the FTP server and its configuration.

FTP and web browsers

Most recent web browsers and file managers can connect to FTP servers. This allows manipulation of remote files over FTP through an interface similar to that used for local files. This is done via an FTP URL, which takes the form ftp://<ftpserveraddress>.  A password can optionally be given in the URL, e.g.:   ftp://<login>:<password>@<ftpserveraddress>.  Most web-browsers require the use of passive mode FTP, which not all FTP servers are capable of handling.