FTP commands: overview of FTP commands

FTP commands allow you to easily transfer and download data. A code is sent in response to FTP commands.

What are FTP commands and what are they used for?¶

Since 1971, the network protocol File Transfer Protocol (FTP), defined by RFC 959, is responsible for transferring files online. FTP initiates downloads and thus regulates data traffic between a terminal and a server or a Fileserver. It operates at the application layer, ie the seventh layer of the OSI model, and can be controlled by special FTP programs like FileZilla. Data transfer takes place through two channels, called control channel and data channel. It is to control this transfer that FTP commands are exchanged between the client and the server. The control channel used for this exchange is TCP port 21.

FTP commands are text-based. Most are defined in RFC 959. In particular, they allow to send, receive, modify or delete files or directories. While many FTP commands are recognized and used by almost all common programs, some FTP commands are only made available by a particular client. These additional commands are intended to improve usability and provide users with even more powerful tools. Requesting FTP commands through the client always results in a response from the server in the form of a code.

What are the most important FTP commands?¶

As already mentioned, the list of possible and existing FTP commands is very long. However, it is not necessary to know them all to use FTP on a daily basis. Here you will find a selection of 25 most important FTP commands, listed in alphabetical order. This list represents a good basis for using this network protocol, in particular for setting up your own FTP server. Some of these commands can also be used when working with the Trivial File Transfer Protocol (TFTP).

The 25 Most Important FTP Commands¶

FTP commands and their RFCs¶

Here you will find an overview of the 25 most important FTP commands and their Requests for Commands (RFC):

What are FTP commands for Linux?¶

It is also possible to use FTP commands under Linux. For example, you can set up an Ubuntu FTP server, configure your own Debian FTP server or even use Linux with a client. In addition to the FTP commands discussed above, there are a few Linux-specific options you can use in command line. These include the following in particular:

• -4: use IPv4 exclusively to contact a host
• -6: use IPv6 exclusively
• -d : activate the debugging function
• -e: prevent command changes and history support
• -g: disables typing generic names for files
• -i: prevent prompts being sent while transferring multiple files
• -n: prevent automatic connection attempts
• -p: switch to passive mode for data transfers
• -v: get all server responses, including transfer statistics

What are the corresponding codes?¶

When you send FTP commands, the server always responds with a code. This consists of a three-digit number and is sent as an HTTP response. The codes are divided into five categories:

• 100-199: if one of these codes appears, the FTP command has normally been executed successfully. However, the server requests another command.
• 200-299: these codes also signal correct execution of the corresponding FTP command. No further action is necessary.
• 300-399: these codes also indicate successful execution of the FTP command. However, other information is required to be able to complete the processing of the order.
• 400-499: if any of these codes appear as a response, the command was not executed. The problem however seems temporary, a new instruction may possibly give a better result.
• 500-599: these codes indicate that the FTP command was not executed. Trying again would result in the same error message.

Summary: Using FTP Commands¶

The FTP commands mentioned above allow you to transfer and download data successfully. This can for example allow you to edit your own website. However, as the username and password are not encrypted with FTP, it is recommended that you use the SSH File Transfer Protocol (SFTP) instead. This is based on FTP, but offers much more powerful protection mechanisms. We also recommend that you check the port beforehand.