FTP (anonymous FTP, heterogeneous connection)

anonymous FTP

 For FTP services, you need to create an account in advance and enter a user ID and password when transferring files.

 In other words, in this method, it is necessary to create an account in advance for the person who uses the FTP service and distribute it to that person.

It cannot be said that it is convenient to use it for the purpose of having it widely used, such as when you want to distribute data.

 Therefore, in FTP, mechanisms for anonymous FTP and file transfer are provided. Anonymous means "anonymous" in English.

 By using "anonymous" as the login user name and your own email address as the password, you can use the FTP service without creating an account.

This mechanism allows an unspecified number of users to use file transfer.

 Web browsers such as Internet Explorer can be used to access anonymous FTP sites without using dedicated FTP client software.

For example, you can access it by entering "ftp://○○○○" in the URL field.

Of course, you can also view the list of files.

 However, since files can now be downloaded using the Web system, the number of sites that use anonymous FTP to publish files is decreasing.

Heterogeneous connectivity via FTP

In FTP, four data types are defined for the data to be transferred.

・ASCII (Text)
・IMAGE (Binary)

By the way, EBCDIC and LOCAL are not used much nowadays.

Broadly speaking, FTP handles two types of data: ASCII and Binary.

 Of these, ASCII (Text) files may appear to be handled as the same data by any model, but they are actually different.

 That's because the line feed code is different for each OS. For this reason, if you forward it as it is, if you receive it on a different model, line breaks will not be performed properly and problems will occur.

Therefore, FTP has a mechanism that allows the OS on the receiving side to convert it to the correct code.

 The mechanism is that the sending side converts the ASCII file to the NVT-ASCII format and sends it, and the receiving side converts it back from NVT-ASCII to the ASCII file in the local environment.

 Binary files don't do this kind of work and send the data as is. By separating files into two types in this way, FTP ensures data compatibility, which is a problem of heterogeneous connections.