Macintosh: Telnet & FTP
The following table is for your reference as you learn about telnet
and FTP:
Term Definition
Client A program you use to request a resource or service from another
program called a "server." For example, you may use a client to
request a file from a file server. Generally, the client is located
on a different computer from the server, often on your own desktop.
See "Server."
Download Simply put, to "get" a file from a server. To be more specific, it
means to transfer files between two computers, usually, to transfer
files from a server on a larger computer to a client on a smaller
computer. See "Upload."
Host A computer, connected to a network, that allows you to log in and use
resources. For example, fog is a host computer you may use for your
email service.
IP Number Internet Protocol number. The unique number that identifies a
computer on the Internet. You can use a computer's name or its IP
number when you specify its address.
Server A program that "serves up" resources and services you request using
your client program. The server is usually located on a "host"
computer. "Host" and "Server" are frequently used interchangeably.
See "Client."
Upload Simply put, to "put" a file onto a server. To be more specific, it
means to transfer files between two computers, usually, to transfer
files from a client on a smaller computer to a server on a larger
computer. See "Download."
We
got help with these definitions from the Free On-line Dictionary of Computing
at http://wombat.doc.ic.ac.uk/.
Telnet and FTP are protocols, a set of formal rules for
transmitting data. You use these protocols to connect to servers on the
Internet for two different purposes:
- To log on to an Internet server and look at information there, you use the
telnet protocol. For example, you use telnet to log on to the library's
server. You cannot download or upload files using telnet.
- To download or upload files, you use the File Transfer Protocol (FTP).
You may already be using telnet to log on to the campus email
server, or to log on to hosts that provide public access, such as the library's
public information server. To telnet to a host from a Macintosh with a direct
Internet connection, you can use a program called NCSA Telnet. You cannot use
NCSA Telnet if you're using a modem, but you can telnet using UNIX commands as
discussed later in this document.
Making a Telnet Connection With NCSA Telnet
To see how NCSA Telnet works, try telnetting to the library server.
Double-click on the NCSA Telnet icon to start the program.
In the Host/Session Name field, type the name or IP number of the host you want
to access.
Then click on the Connect button. If your
connection is successful, your host session begins.
To gain access to the host, you now provide a user ID or name, and, on many
hosts, a password. If a host offers public access, this screen usually
displays the required user ID and password.
You can download NCSA Telnet from ftp://ftp.ccsf.org/pub/TCP/.
Moving Around and Exiting
The way you move from screen to screen in a telnet session varies
from host to host. You often find this navigation information displayed at the
bottom of the screen. Many hosts provide a menu structure that's easy to use,
but some do require you to use UNIX commands. If you're having difficulty in a
session and can't find help on the screen, try typing help. If you want
to exit the session but can't find the command, try typing exit. After
you exit from one host session, you may want to telnet to another host using
NCSA Telnet. Select Open Session from the File menu, and
complete the pop up window again. When you've completed all your sessions, you
can quit NCSA Telnet by selecting Quit from the File
menu.
Making a Telnet Connection With the UNIX Command
Once you connect to a host, you can telnet to a different host
using the UNIX command "telnet". If you have a direct Internet connection,
it's preferable to use NCSA Telnet instead to conserve Internet resources. If
you're using a modem, however, you'll want to use UNIX to telnet to "foreign"
hosts. First connect to your campus server with a communications program such
as MacKermit or ZModem. Then at the UNIX prompt, type
telnet hostname
Telnet's Limitation
You can get access to a great deal of information and services
through telnet, but you cannot transfer files. To transfer files, use the File
Transfer Protocol (FTP), which is discussed next.
You can use FTP to transfer files between:
- Your computer and a server on which you have an account
- Your accounts on two different servers
- Your computer (or account) and an "anonymous FTP" server
Anonymous FTP servers allow you to log on and transfer files, even though you
don't have an account on the servers. Let's look at some reasons you might use
FTP.
If you have an account on a server on campus, you can use FTP to upload
files from your PC to your account. With the file in your account, you might
then want to email it, for example. Downloading files through
anonymous FTP is a good way to get free software and other types of files.
(Note: before you run any software you download, be sure to check it for
viruses. When you download text files, however, you don't need to worry about
infecting your computer with a virus; viruses are transmitted only through
program files. Some servers also allow the public to upload files to selected
directories--which is why you need to be careful about viruses when you
download programs.)
Two Kinds of FTP
For FTP on the Macintosh, you can use a package called Fetch, or
use UNIX commands. Fetch is a microcomputer software package that you'll put
on your Mac hard drive. Although it can only be used with a direct
("hard-wired) connection (i.e. not with a modem connection), Fetch has distinct
advantages over UNIX ftp. Unix ftp is a mainframe client. This means that you
can connect via modem to a host like fog and ftp files to your account there.
Both kinds of ftp are discussed below.
First Things First: Connect to a Host
If you have a direct ("hard-wired") Internet connection, you can
use Fetch to transfer files between a server and another computer connected to
the Internet. To start Fetch, double-click on the Fetch icon. This dialog box
pops up:
Use the dialog box to log on to the host you choose. Type the name or IP
number of the host in the Host field. Next, complete the User ID and Password
fields in one of two ways:
- To log on to a host on which you have an account, complete the User ID and
Password fields with the appropriate information for your account.
- To log on to a host that allows anonymous FTP, type anonymous in the
User ID field, and type your email address in the Password field.
To go immediately to the directory you want, you can complete the Directory
field, but you must type each letter in the correct case (lower = abc, upper =
ABC). It may be easier to move through the directories after you make your
connection. When you're ready, click on OK.
Downloading and Uploading Files
When Fetch connects to the host, you'll see a window like this one:
You can move around in the server's files by changing the current directory
(click on the box displayed above the list of files), and by double-clicking on
the different folders to display their contents. Notice that you can either
"Get" (download) a file from a server, or "Put" (upload) a file on a server.
Steps for Downloading
To download, do the following:
- Select the file, group of files, or directory you want.
- Specify the file type by selecting Automatic, Text, or Binary.
- For plain text files, select either Automatic or Text.
- For program files, select Binary. If you're unsure of the file type,
try Binary.
- Click on Get. A window pops up that allows you to save the file.
- Select the file's destination, and click on Save.
Making Files Usable
Often the files you download will be compressed so that they take
up less disc space. You have to expand these files before you can use them. A
program called Stuffit expands and installs most compressed files for the
Macintosh.
Steps for Uploading
The process for uploading files with Fetch is similar to
downloading:
- Connect to a host. Usually you'll connect to a server on which you have
an account, such as your email server. If that's the case, be sure to log on
using your own user ID and password, rather than logging on as anonymous.
- Locate the directory on the server where you want to put your
file.
- Click on Put. A window pops up showing files available to you locally:
-
- Select the file, files, or directory you want to put onto the server
(upload). Then click on Open. This window pops up:
- Now you can save a copy of the file to the directory you chose on the
host. You may want to change the file name or format. Consider your options
carefully before you change the file format. In the example shown, we're
uploading a regular Microsoft Word document. Fetch automatically specifies the
format as MacBinary II, which preserves any formatting in the document. You
may have a reason to change the format to Text; for example, if you want to
read the file into the body of an email message, rather than attach it as a
separate file. All formatting is lost, but the document is readable. For more
information about the other file formats, look at Fetch's on-line help (Fetch
Help under the Windows menu).
- When you click on OK, Fetch completes the uploading
process.
Fetch Menu Commands
The following table below lists some ways you can customize your
Fetch session.
If you want to . . . then choose and select . . .
this menu . . .
See file sizes, the date files Remote View File List
were last saved, and other
detailed file information
Preview the contents of a Remote View File
file; select the file and . . .
Select files from different Remote Put Folders and Files . . .
folders to download
Specify a Host connection that Customize Edit Shortcuts
comes up automatically when
you start Fetch (default
connection)
For
more options, refer to Fetch Help.
Closing Your Connection
Click on Close Connection in the Fetch main window to close your
connection to a host. If you're visiting an anonymous FTP server, it's
especially important that you close your connection as soon as you've
transferred the files you need. FTP servers limit the number of connections
that can be made at any one time, so you open up a space for someone else when
you close your connection. When you've completed all your sessions, you can
quit Fetch by selecting Quit from the File menu.
You may want to use UNIX commands to transfer files if, for
instance, you're using a modem. The following table lists some commands you'll
use:
Command Description
ftp ftpservername Opens an FTP session at the server you specify.
binary Sets the file transfer type to binary. Critical to the
successful transfer of files such as Word documents,
graphics, or software packages; also works fine with text
files (files that contain only ascii text and no
formatting).
get filename Transfers the file you specify to your account on the
campus server.
mget file1 file2 Transfers multiple files you specify to your account on the
campus server.
ls Lists all the files in your current subdirectory (folder in
Mac lingo).
cd subdirectory Changes the directory. To move back up to a previous
level, use "cd .." (note the space). This is the
equivalent of double-clicking on a folder.
put filename Transfers a file from your account on a server to a
directory on another server.
mput file1 file2 Transfers multiple files from your account on a server to a
directory on another server.
pwd Tells you the present working directory, or in Mac lingo,
the current folder.
<control>+h Deletes a character to the left of the cursor (acts as a
backspace). Note: use the control key; don't type the
word "control".
help command Displays the definition of a command. Type "help" to see a
full list of valid commands.
bye Ends the FTP session.
Steps for Downloading
Here are the steps for downloading a file using UNIX commands:
- Connect to your campus server.
- At the UNIX prompt, type ftp ftpservername. To use the
example from our discussion of Fetch, we type ftp ftp.ccsf.org. Note:
often "ftp" will be the first level of the server name as well as the command you
use to establish an ftp connect; be sure that you do not omit it in either case.
- Log on to the FTP server.
- If you don't have an account on the server, log on as anonymous. Use
your email address as the password.
- If you have an account on the server, log on with your ID and password.
If the server is available, the ftp prompt appears.
- Find the file you want. Refer to the previous table for commands you'll
need. To continue our example:
- To see the name of the current folder, type pwd.
- To change to the Netscape directory, type cd pub/Netscape.
- To see the files listed in that directory, type ls.
- Type binary to set the file transfer type.
- Type get filename. The file is transferred to your account on
the campus server. To get the file in our example, we type get
netscape3.02Gold.hqx.
- To move the file from the campus server to your computer, use Fetch or, if
you're on a modem, use Kermit.
Uploading
Uploading files is a similar procedure. To upload a file, telnet
to the campus server from which you want to transfer a file to another
server. Note the name of the file you want to transfer. FTP to the target
server and log on. Find the directory to which you want to transfer the
file. At the FTP prompt, type put filename. The file is
transferred.
You can also transfer files on the World Wide Web using FTP. Details of
the FTP session vary with the browser you use, but generally, you simply point
and click to select a file to download. Of course, the file must be available
at an FTP server for you to be able to download it. The browser steps you
through choices for downloading, depending on your computer setup.
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