File Transfer via FTP
One of the most common uses of FTP has been to retrieve or download software,
large documents, graphics, or sound files from
software vendors' sites or
public archive sites on the Internet. Though FTP downloads are still available, many resources that used to be available via FTP have now migrated to the Web. For example, Penn's supported software can now be downloaded directly from the Supported Products site on the Web rather than by using an FTP client program like Fetch or FileZilla. FTP
is also used to upload files to a host computer on which an individual has an account. Web information providers, for example, typically FTP files to the servers on which their sites are located.
Important: Be aware that any software you
download from a remote source could be infected with a computer virus
or other pernicious
program. Protect your data by installing up-to-date antiviral software
on your computer. The University makes available antiviral software for
Windows
machines and Macintoshes at no charge. For information about
obtaining the current versions of this software, check Penn's site devoted
to virus information or speak to your
Local Support Provider (LSP) or
residential Information
Technology Advisor (ITA).
FTP operates in two modes: secure and anonymous. In secure mode, authorized
users must specify an ID and password to retrieve ("get") files from,
or send ("put") files to, remote computers. In anonymous mode, "guests"
can log on to servers storing files available to the Internet public in
order to transfer those files to their own machine or account. You can
access these sites by identifying yourself as a user named "anonymous"
and entering your e-mail address as your password.
Once you're connected to the network, you can run easy-to-use FTP client software on your computer to transfer files between your desktop and a remote computer. The supported FTP clients at Penn are
Fetch for Macintosh and FileZilla for
Windows PCs. Both provide graphical
user interfaces for accessing and navigating FTP servers and hosts.
To initiate a file transfer, locate the command for making a new connection and simply specify the full Internet address of the host computer
you wish to access. Then enter your account ID and password if you are
accessing a secure service, or type anonymous and enter your complete
e-mail address if you are logging on to a public server as a guest. You
should then be connected to the server and able to navigate directories
and retrieve and/or upload files. Some services at Penn, such as www.upenn.edu, have switched to Kerberized FTP. Authorized users of such services must first obtain a Kerberos ticket, identify themselves using their PennKey and password, and then access the server using their FTP client. General information on working in a Kerberized environment can be found on the PennKey web site.
FTP from within Dreamweaver
Dreamweaver, the supported
software package for Web authoring and site management, has a built-in
FTP client that Web information providers can use to upload and download
files to their Web servers without exiting from Dreamweaver. Unfortunately,
Dreamweaver's built-in FTP cannot be used to upload or download files
to Kerberized Web servers such as www.upenn.edu. Workarounds are, however,
available for Windows and Macintosh users: Proxies created by University
of Washington (Windows) and Iowa State University (Macintosh) enables
them to employ the built-in FTP clients contained in web-authoring tools
such as Dreamweaver. Information on obtaining
and configuring both proxies is available.
FTP from within a Web browser
Many Web browsers have FTP capability built in and can be used to access and navigate FTP servers and
hosts. If you click on an FTP resource on a Web page, a file transfer
will be initiated automatically. You need not know the address of the
resource, and you will be asked to identify yourself only if you are accessing
a secure site. You can also use a web browser to navigate directly to
an FTP site, directory, or file by entering its complete URL in the browser's
location field and pressing Return. For FTP, the URL format is ftp://<site, directory, or filename> rather than http://<site, directory, or filename>. Note, however, that many
people prefer to
use FTP software rather than a browser because transfers initiated with
FTP software are often faster. FTP software is also required to FTP to a Kerberized service; it is not possible to FTP to a Kerberized service from within a Web browser.
Before you transfer a file, it is useful to know whether or not you can
use it on your system. That means you have to know what application and
computer platform (e.g., Macintosh or Windows) the file was written for.
Documents or directories with multiple
files are often combined into one "archive" file for ease of transfer,
and large archive files are often compressed to reduce transfer time and
disk space requirements. The standalone utilities StuffIt (Macintosh and
Windows) and PKZip (Windows) are often used to provide file archiving
and compression.
Clues to the platform, application, and archiver or compressor often come from
file name suffixes, called extensions; from explanations in READ.ME files
listed in the directory in which a file is stored; or from information on the
Web page from which you access an FTP resource. The following are a few of the
most common extensions and the formats they represent:
| .exe |
Windows application or self-extracting archive
|
| .gif |
Graphic Interchange Format
|
| .html |
Document in HyperText Markup Language
|
| .hqx |
Macintosh BinHex file archive
|
| .jpg |
Joint Photographic Experts Group image format
|
| .pdf |
Document in Adobe Portable Document Format
|
| .ps or .eps |
Document in PostScript format
|
| .sea |
Macintosh self-extracting archive
|
| .sit |
Macintosh StuffIt file archive
|
| .tar |
UNIX archive file
|
| .txt |
Document in ASCII text format
|
| .zip |
Compressed (zipped) DOS/Windows format
|
Unless a file is self-extracting, you need a copy of the appropriate
archiving/compressing software to "unarchive" or "decompress" a file after
transferring it. The supported software packages to accomplish this,
Stuffit
Expander for Macintosh and Windows, are available from
the supported products Web site. Expander will automatically recognize and decompress most
common compressed formats.
If you are navigating to a server (rather than clicking on a specific
FTP resource from a Web page), it also helps to know ahead of time its
general contents and how the server directories are organized. World
Wide Web search engines can help you track down a topic or determine whether you are the audience
for a file, group of files, or specific anonymous FTP file server.
Many FTP server administrators request that you not access their archives between 9 AM and
5 PM local time, to ensure that their own community has preferred access to local
services. Please honor the request (assuming you can determine what the time is
at that site).
Related resources
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