File Transfer Protocol

File Transfer Protocol is a network protocol that was specified in 1985 for the purpose of file transfers.

Using the File Transfer Protocols

File Transfer Protocol (short: FTP) is used to exchange files between a server and a client. Several configurations may apply:

From server to client (download a file)
From client to server (upload a file)
From one server to another server (file sharing using the File Exchange Protocol)

Once a connection has been established, files can not only be uploaded and downloaded, users can also use FTP to create, change, read, or delete directories. Files can be renamed, moved, or deleted. Moreover, FTP allows permissions management for files. Thus, you can determine whether stored files may be read, altered, or executed only by the owner, a particular group, or the public. These authorization structures are represented by a three-digit numerical value. The value “777,” for example, means that anyone can access, modify, or execute the files.

Establishing an FTP session

You can establish an FTP session with a TCP connection. The client sends commands to the desired server. There are two types of FTP modes, active and passive. In “active mode,” the client takes initiative and opens a port. It then contacts the server and informs it of its own IP address and the selected port. All communication of the two partners is carried out via a control port, so that parallel file transfers are possible.

In “passive mode,” however, the client requests the server to open a port itself through a PASV- or EPSV command. The server then opens a port and returns to the client a response containing the port and the server’s IP address. This allows a connection to be made. The passive method is usually used when a server-side connection is not possible because access to the client is prevented by a firewall.

Anonymous FTP access

For FTP servers that are accessible to the public, there is usually a user account that can be used by anyone. It is often referred to as “Anonymous.” Anyone logging in with this account, does not have to enter a password. This approach is common, for example, with mirrors or the university servers, where a large number of users must access it.

Connection establishment through software

To connect via the File Transfer Protocol, the user needs an FTP client. This can be accomplished with a separate software that is installed on the computer. Many users simply rely on the FTP client that has been integrated in most browsers. With the following special syntax an FTP server can then be addressed directly in the web browser,

 ftp://[ftp_username[.ftp_PWD]@]Servername[:Port]

Alternately, the services of WebFTP can be resorted to. This is an FTP client that can be executed and displayed in the web browser. It allows you to navigate in the directories from within the browser.

To establish a connection using an FTP client, you first have to log in. To this end, you need to specify the FTP server address or the corresponding IP address and the port and then connect with your user name and password.

Relevance to search engine optimization

As an SEO you will not be able to get around FTP. As part of website optimization, the web server needs to regularly accessed to record new data, for example, plug-ins or SEO optimized website themes.