What are the FTP Operations?

When using File Transfer Protocol (FTP), the user implements some or all of the following operations −

Connecting to a remote host

To implement a file transfer, the user begins by logging into the remote host. Four commands are used.

• Open selects the remote host and sets up the login session.
• User recognizes the remote user ID.
• Pass authenticates the client.
• Site sends data to the foreign host that is used to provide services specific to that host.

Navigating the directory structure

After a client has been authenticated and logged on to the server, that client can navigate through the remote host's directory structure to locate the file desired for retrieval or locate the directory into which will transfer a local file.

The subcommands that execute these services are as follows:

• cd Changes the directory on the private host. A pathname can be determined but must conform to the directory structure of the remote host.
• Icd Change the directory on the localhost. It is equal to the cd command. A pathname can be determined but must conform to the directory structure of the localhost.
• Is Lists the contents of the remote directory
• dir Lists the contents of the private directory. It is similar to the ls command; the list generated by dir is treated as data and requires a data connection.

Controlling how the data is transferred

Transferring data between dissimilar systems often involves the transformation of the data as part of the transfer process. The three aspects of transfer can be the mode of the bits, representation of the data and file structure. Modes of data transfer can be block mode (B) and byte stream mode (S). Representation of data can be ASCII based or EBCDIC based.

A file structure can be a continuous sequence of a data byte, sequential record, or file made up of pages.

Transferring Files

It can use the following commands to copy files between FTP clients and servers.

• get Copies of a file from the remote host to the localhost.
• mget Copies various files from the remote to the localhost.
• put Copies of a file from the localhost to the remote host.
• mput Copies multiple files from the localhost to the remote host.

Terminating the FTP session

It can use the following commands to end an FTP session

• quit − It can disconnect from the remote host and removes FTP. Some implementations use the BYE subcommand.
• Close − It can disconnect from the remote host but leaves the FTP client running.

It can issue an open command to establish a new control connection.