File Transfer Protocol -FTP

Introduction

File Transfer Protocol, FTP was first proposed on April 16, 1971 by Abhay Bhushan for and developed for implementation on hosts at MIT and was later defined by RFC 959 published in 1985.

File Transfer Protocol (FTP) is the protocol that actually lets us transfer files, and it can accomplish this between any two machines using it. As a user, you can use FTP with a simple command line interface (for example, from the Windows MS-DOS Prompt window) or with a commercial program that offers a graphical user interface.. It is also important to realize that FTP is insecure. When your username and password are sent to the server they're both sent as plain text and could be intercepted and read. 

If your server supports SFTP or FTP with TLS encryption, we suggest one of them instead of plain FTP to help keep your information private.

Accessing a host through FTP is only the first step, though. Users must then be subjected to an authentication login that’s probably secure.
Though what you’ll gain access to will be limited. Even when employed by users manually as a program, FTP’s functions are limited to listing and manipulating directories, typing file contents, and copying files between hosts. It can’t execute remote files as programs.
 with passwords and usernames implemented by system administrators to restrict access. You can get around this somewhat by adopting the username anonymous.

How It Works

TCP and IP are the two major protocols that keep the internet running smoothly. TCP manages data transfer while IP directs traffic to internet addresses. FTP is an underling of TCP and shuttles files back and forth between FTP server and FTP client. Because FTP requires that two ports be open--the server's and the client's--it facilitates the exchange of large files of information.

First, you as client make a TCP control connection to the FTP server's port 21 which will remain open during the transfer process. In response, the FTP server opens a second connection that is the data connection from the server's port 20 to your computer.

Using the standard active mode of FTP, your computer communicates the port number where it will stand by to receive information from the controller and the IP address--internet location--from which or to which you want files to be transferred.

If you are using a public--or anonymous--FTP server, you will not need proprietary sign-in information to make a file transfer, but you may be asked to enter your email address. If you are using a private FTP server, however, you must sign in with a user name and password to initiate the exchange of data.

Modes of File Transfer

Three modes of transferring data are available via FTP.

The system can use a stream mode, in which it transfers files as a continuous stream from port to port with no intervention or processing of information into different formats. For example, in a transfer of data between two computers with identical operating systems, FTP does not need to modify the files.

In block mode, FTP divides the data to be transferred into blocks of information, each with a header, byte count, and data field.

 In the third mode of transfer, the compressed mode, FTP compresses the files by encoding them. Often these modifications of data are necessary for successful transfer because the file sender and file receiver do not have compatible data storage systems.

Passive FTP

Should your computer have firewall protection, you may have difficulties using FTP. A firewall protects your PC by preventing internet sites from initiating file transfers. You can circumvent your firewall's function by using the PASV command that reverses the FTP process, allowing your computer to initiate the transfer request.

Many corporate networks use PASV FTP as a security measure to protect their internal network from assaults of unwanted external files. Also called passive FTP, the process requires that any transfer of information from the internet or other external source must be initiated by the client or private network rather than the external source.

Passive FTP mode is used by some newer FTP servers on the Internet to better work with firewalls. Microsoft Internet Explorer includes a setting for Passive FTP (sometimes called "PASV") mode. You may need to either enable or disable this setting to allow Internet Explorer to work as an FTP client with a given FTP server. Follow these instructions to make it happen.

Here's How:

1.    Open Internet Explorer from the Start Menu or command line.

2.    On the Internet Explorer menu, click Tools to open the Tools menu.

3.    On the Tools menu, click Internet Options... . A new Internet Options window will appear on the screen. 

4.    In the Internet Options window, click the Advancedtab.

5.    First, find the setting called Enable folder view for FTP sites (located near the top of the list of settings). Ensure this feature is disabled (unchecked). Passive FTP mode in Internet Explorer will not work unless this feature is disabled.

6.    Next, find the setting called Use Passive FTP (located approximately halfway down in the list of settings).

7.    To enable the Passive FTP feature, set the checkmark in the box next to the Use Passive FTP setting. To disable the feature, clear the checkmark. Alternately set and clear the checkmark by clicking once inside the checkbox.

8.    Click OK or Apply to save the Passive FTP setting.

Tips:

1.    It is not necessary to reboot your computer to enable or disable Passive FTP.

Further FTP Security

In response to the need for a more secure transfer process for sensitive information such as financial data, Netscape developed a Secure Sockets Layer (SSL) protocol in 1994 that it used primarily to secure HTTP--HyperText Transfer Protocol--transmissions from tampering and eavesdropping. The industry subsequently applied this security protocol to FTP transfers, developing SFTP, a file transfer protocol armored with SSL for protection from hackers.

FTP Commands

!	Using this command you will have the capability of toggling back and forth between the operating system and ftp. Once back in the operating system, typing exit will take you back to the FTP command line.
?	Access the Help screen.
append	Append text to a local file.
ascii	Switch to ASCII transfer mode
bell	Turns bell mode on or off.
binary	Switches to binary transfer mode.
bye	Exits from FTP.
cd	Changes directory.
close	Exits from FTP.
delete	Deletes a file.
debug	Sets debugging on or off.
dir	Lists files if connected. dir -C = Will list the files in wide format. dir -1 = Lists the files in bare format in alphabetic order dir -r = Lists directory in reverse alphabetic order. dir -R = Lists all files in current directory and sub directories. dir -S = Lists files in bare format in alphabetic order.
disconnect	Exits from FTP.
get	Get file from the computer connected to.
glob	Sets globbing on or off. When turned off the file name in the put and get commands is taken literally and wildcards will not be looked at.
hash	Sets hash mark printing on or off. When turned on for each 1024 bytes of data received a hash-mark (#) is displayed.
help	Access the Help screen and displays information about command if command typed after help.
lcd	Displays local directory if typed alone or if path typed after lcd will change local directory.
literal	Sends a literal command to the connected computer with an expected one line response.
ls	Lists files of the remotely connected computer.
mdelete	Multiple delete.
mdir	Lists contents of multiple remote directories.
mget	Get multiple files.
mkdir	Make directory.
mls	Lists contents of multiple remote directories.
mput	Sent multiple files
open	Opens address.
prompt	Enables or disables the prompt.
put	Send one file
pwd	Print working directory
quit	Exits from FTP.
quote	Same as the literal command.
recv	Receive file.
remotehelp	Get help from remote server.
rename	Renames a file.
rmdir	Removes a directory on the remote computer.
send	Send single file.
status	Shows status of currently enabled and disabled options
trace	Toggles packet tracing.
Type	Set file transfer type.
user	Send new user information.
verbose	Sets verbose on or off.