The File Transfer Protocol, or FTP, is used for transferring files from one machine to another on the Internet. FTP requires that a user be logged in to both hosts.

Anonymous FTP is a special use of FTP in which a site makes its collection of files available to users who do not have accounts on that host. The anonymous FTP convention uses a special login name of anonymous and a special password, usually one's email address, to let users have limited access to the remote host for the purpose of retrieving files that have been approved for public access. It is really a "guest" activity rather than an "anonymous" activity.

• How FTP Works
• How to Get FTP
• Pros and Cons
• How to Use FTP
• Key Commands
• What FTP Looks Like
• Trying FTP
• For Further Information
• Contacting the NAIC

FTP is based on the client-server model where the client sends queries and the server sends back responses to the queries. To accomplish file transfers, there must be a client program on the local host and a server program on the remote host.

The FTP client provides the user with a session that enables him to send commands to the remote host machine. The server provides access to directories containing files that may or may not be open to an anonymous account. The user may browse through the directories and files, transfer files and issue a number of commands to the server. Normally, files on the host machine are organized in a hierarchical fashion, with a parent directory at the top and branches of subdirectories containing files below that. FTP expects the user to know the name and location of the file that is to be retrieved. Many sites urge users to retrieve and read README files first before proceeding to retrieve other files from a directory.

Internet sites that permit anonymous FTP logins allow guest users to do only a limited number of operations, such as logging in using FTP, listing the contents of certain directories, and retrieving files from those directories.

How to Get FTP

Most Unix Internet connections come standard with FTP software. Usually, it is the system administrator who installs and maintains this software. Software is also available for PCs and Macintoshes. The Macintosh client, called Fetch, is available from Dartmouth College. Information may be obtained by sending email to Fetch@dartmouth.edu.

Pros and Cons

The most widely recognized advantage of FTP is its availability. Since it is usually standard with most Unix Internet connections, it is probable that every system of this type will have FTP capabilities (however, not all may have anonymous FTP capabilities).

FTP is the easiest way to retrieve the many files from various repository hosts (see the list below) and this can be accomplished using the anonymous FTP convention.

A disadvantage of FTP is that its interface is not always very user-friendly. To retrieve a file, the user needs to know what host it is on and the pathname of the file, i.e. the directory where it is located along with the specific filename of the file.

How to Use FTP

To start an FTP session, the user must establish a network connection from his local host to the remote host. On many Internet hosts, the user types ftp and the host name of the machine to which he wants to connect. Macintosh users begin their sessions by clicking on the Fetch icon.

The remote host prompts the user for a username and a password. When using anonymous FTP, the user enters anonymous as the username and his email address as the password. Otherwise, the user types in the userid and password for his account on that host.

Key Commands

After logging on, the user might receive a welcome message from the host machine, and then the FTP prompt, ftp>. Macintosh and PC Windows users will use a graphical point and click interface. The following basic commands may be used with Unix and PC DOS clients:

To:                                     Type:

List the directory to the terminal......ls or dir
Change directories (move up or down)....cd or cdup
Retrieve a file.........................get <filename>
Put a file on the host machine..........put <filename>
Abort a file transfer...................CTRL-C
Get help/list of commands...............help or ?
Leave the FTP session...................exit, quit or bye

Many hosts maintain files named README or INDEX. These files usually contain information about the host and its directories and files. It is usually a good idea to retrieve these files first and read them before continuing, especially if the host's directory has a large number of subdirectories and files.

What FTP Looks Like

Here is an example of a typical FTP session from Unix client. In this session, the user connected to the host naic.nasa.gov, logged on as anonymous and entered her email address when prompted for a password. She then retrieved the file named README. Notice that this FTP server provides helpful introductory comments.

-------------------------------------------------------------------------------
% ftp naic.nasa.gov
Connected to naic.nasa.gov.
220 naic.nasa.gov FTP server (Version wu-2.1c(5) Tue Dec 14 08:21:13
PST 1993) ready.

Name (naic.nasa.gov:mstahl): anonymous
331 Guest login ok, send your complete e-mail address as password.
Password:
230----------------------------------------------------------------------------
230-Welcome to the NASA Network Applications and Information Center FTP
Archive
230-    
230-     Access to NAIC's online services is also available through:
230-
230-        Gopher         - naic.nasa.gov (port 70)
230-    World-Wide-Web - http://naic.nasa.gov/naic/naic-home.html
230-
230-        If you experience any problems please send email to 
230-
230-                    naic@nasa.gov
230-
230-                 or call +1 (800) 858-9947
230----------------------------------------------------------------------------
230-
230-Please read the file README
230-  it was last modified on Fri Dec 10 13:06:33 1993 - 111 days ago
230 Guest login ok, access restrictions apply.
ftp> get README
200 PORT command successful.
150 Opening ASCII mode data connection for README (5641 bytes).
226 Transfer complete.
local: README remote: README
5783 bytes received in 0.028 seconds (2e+02 Kbytes/s)
ftp> bye
221 Goodbye.
% 
-------------------------------------------------------------------------------

Trying FTP

Here is a list of some FTP sites that allow anonymous FTP logins:

Library-related files                   hydra.uwo.ca
                                        infolib.murdoch.edu.au
                                        ftp.uni.edu
                                        ftp.cni.org

Network information                     is.internic.net
                                        naic.nasa.gov
                                        nic.ddn.mil

Microcomputer software repository       wuarchive.wustl.edu

Macintosh software repository           sumex-aim.stanford.edu

For More Information

Books that contain extensive descriptions of FTP are:

The Whole Internet Users Guide and Catalog by Ed Krol. O'Reilly and Associates. 1992.

The Internet Passport, published by NorthWestNet. 1993.

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Questions?

If you have any questions about this material, please contact the NAIC:

HOW TO CONTACT THE NAIC


Telephone               1-800-858-9947  (toll-free within US)
                        1-415-604-0600  (outside US)


Staff are available to answer the phone from 6 a.m. to 5 p.m.
Pacific time.  Voicemail messages left at other times will be
promptly returned.


FAX                     1-415-604-0978


Electronic Mail

   From an Internet host send mail to:
         naic@nasa.gov
   From a DECnet host send mail to:
         EAST::"naic@nasa.gov"

Online servers:
   URL:gopher://naic.nasa.gov
   URL:http://naic.nasa.gov/
   URL:ftp://naic.nasa.gov/

Postal Mail
   NAIC
   NASA Ames Research Center
   M/S 204-14
   Moffett Field, CA 94035-1000

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