CHAPTER 6 -
Telnet & FTP - Connecting to Other Computers & Getting a File from
There to Here
6.1 Introduction to Telnet
In other
chapters of this book, you have connected to other computers by traversing
menus using gopher or by using one of the www browsers. Often you might want to connect directly to
another computer for services that are not provided on your computer. For example, one of the authors does not
have a mail server on his PC. He needs
to connect to another computer to read and send mail. One of the ways of connecting to another computer on the Internet
is using the Telnet protocol. Telnet
was one of the first protocols developed for the Internet. It was designed to allow users around the
world to use computers located at remote sites. The program telnet is
designed to make use of this Telnet protocol.
Today telnet is used to by individuals to log
into other computers that they have accounts on. Telnet is also used to
log into computers that provide access to services such as library catalogs,
Internet resources like gopher or archie, or other facilities that can be
made available to others. With the
increased use of the World-wide Web, less emphasis is being placed on using telnet to connect to other computers.
6.2 How to Use Telnet
6.2.1 Internet Addresses
Before you can
connect to another computer, you must know its Internet address. All Internet hosts have two kinds of
addresses. Most of the time you will be
able to use the domain address that is written in text, e.g. www.jaring.my. Domain addresses usually have at least three
parts. The last part is either a
two-letter geographic top-level domain or an organizational top-level domain
(See Fig. 6.1). The next to last part of the address is a sub-domain that
generally represents the institution.
The leftmost sub-domain of the address usually represents a computer at
the institution. So the address
www.jaring.my represents the computer running the www server at the jaring
institution in Malaysia.
Underlying the
domain address is another address called the IP (Internet Protocol) address.
This address is a numeric address represented as four numbers separated by
periods. When you attempt to access a computer using its domain address, the
address is converted into the corresponding IP address and then the connection
is made. For example, if you were to telnet to www.jaring.my, the domain address would be converted to the IP
address 192.228.128.16. You can use the IP address anywhere that you
would use the domain address. There may
be a few occasions where a domain address will not be recognized and you will
have to use the IP address.
6.2.2 The Telnet Program
To use Telnet,
you need to run a program often called telnet
on your computer. This program uses the
Internet to connect to the computer you have specified. You can either run the telnet program by typing telnet
with no arguments, or by typing telnet followed by the name of the host you are
connected to on the command line- telnet
www.jaring.my. If necessary, you may
have to follow the domain address with a port number.
Domain Meaning
com commercial
edu educational
gov government
int international
organizations
mil military
net networking
organization
org non-profit
organization
au Australia
ch Switzerland
("Confoederatio Helvetia")
de Germany
("Deutschland")
es Spain
("Espana")
jp Japan
my Malaysia
sg Singapore
tw Taiwan
uk United Kingdom
us United States
Fig.
6.1Examples of Top-Level Domains
If you only
type telnet on the command line,
your computer's prompt will change to telnet>
and you will need to use the open
statement to connect to another computer on the Internet, e.g.
telnet> open www.jaring.my
The first few
messages you see will be messages from your computer. These will be followed by messages from the remote computer. Usually you will be asked to enter your a
user-id and password. (See Fig. 7.2)
Some of the public telnet sites will
allow you to access them without a user-id and password. Once this happens, you are logged onto the
remote computer and can use all of the instructions that are appropriate for
the remote computer.
When you are
finished using the remote computer, you should log-out. This often does not close the connection
between your computer and the remote computer.
If you are still connected to the remote computer, you can break the
connection by pressing CTRL-]. This
will return you to the telnet>
prompt. You can then connect to another
computer using the open statement or quit and return to using your own
computer. If you run into trouble, the
question mark (?) will bring up a list of available commands.
-VE>
telnet ppp.itm.my
Trying...192.228.170.5
Connected
to PPP.ITM.MY.
Escape
character is '^]'.
SunOS
UNIX (pppitm)
login:
wayne
Password:
**************
Last
login: Fri Jun 16 05:51:38 from venus.nmhu.edu
SunOS
Release 4.1.3 (GENERIC-MAR17) #1: Fri Mar 17 09:03:22 SST 1995
Fig.
6.2 - Logging into another computer using telnet
Occasionally,
you will not be able to connect to a remote site. If you incorrectly type the domain address, you will see an error
message as shown in Fig. 6.3. Sometimes the remote computer may not be running
or all the lines may be busy. If this
happens, you will typically see a message like the one shown in Fig. 6.4.
-VE>
telnet newton.dip.anl.gov
%UCX-E-TELNET_GETHST,
Error in getting host name
Fig. 6.3 -
Incorrect address
-VE>
telnet irc.nsysu.edu.tw
Trying...140.117.11.33
%UCX-E-TELNET_CONECT,
Failed to connect to remote host
Fig. 6.4 -
Cannot connect to remote computer
When you
connect to a remote computer, you will often be asked to enter a terminal
type. In the early days of computing,
most users worked at terminals connected to the mainframe or minicomputer. Today to connect to many servers, you need
to emulate one of these types of terminals.
This is done using a terminal emulation software package. The most common ones are DEC's (Digital
Equipment Corporation) VT100 and VT220.
If the remote computer asks for a terminal type, try one of these first. If neither works, try TTY which is the
standard for teletypes.
In a few
cases, telnet will not work. If a computer is an IBM mainframe, it will
expect you to use the program tn3270. You can usually identify these by the VM or MVS in the introductory messages from the remote computer. When you see this, try typing tn3270 instead of telnet.
Fig. 6.7 -
TELNET Connect window
Fig. 6.8 -
Using TELNET to connect to a remote host
WinQVT is just
as easy to use and contains facilities for connecting to ftp and UseNews. After
pressing the WinQVT icon, an introductory window will be displayed (Fig.
6.9). Either press the terminal icon or
select telnet from the File
menu. A connection window will be
displayed (Fig. 6.10). After inserting
the host domain name or IP address, and pressing OK, you will be connected to
the remote host (Fig. 6.11).
Fig. 6.9 -
WinQVT Introductory window
Fig.
6.10 - WinQVT connect window
6.4 Introduction to FTP
FTP (File
Transfer Protocol) is a set of rules for transferring files between computers,
usually connected through the Internet.
If your computer supports FTP and is connected to the Internet, then you
can access a large number of computer systems containing a large number of files. This facility was one of the main reasons
for the initial popularity of the Internet. The program that supports the
transfer of files using FTP is ftp. You can access information on virtually any
topic using ftp. In addition, you
can access a multitude of archives of software for most computer systems (DOS,
UNIX, Macintosh, etc.).
FTP uses the
client / server model that was discussed with gopher. Both client and server computers need to be running the ftp software. Unfortunately most of the non-Windows versions of ftp are not particularly easy to
use. Ftp sites can also be connected to
using Netscape and Internet Explorer, but only for downloading of files.
Fig.
6.11 - Connecting to remote host using WinQVT
6.5 How to Use FTP & Anonymous FTP
To use ftp, you need to know the address of
the FTP site you want to access. To
connect to an FTP server, type ftp
<server address> where server address is either the domain name
or IP address of the FTP server (Fig. 6.12).
If you only type ftp, your
computer will display the FTP prompt, and you will be expected to use the open command followed by the server address. Many of the servers will
then display a lot of information about the site while others will only
identify the site.
There are two
ways to connect to the FTP server. If
you have account on the server, you can log on normally and access any of the
files in your account. In most cases
however, you will be using anonymous ftp. To use anonymous
ftp, you will type in "anonymous" as the login name and type in
your e-mail address as the password for the server computer. Most FTP servers
will accept anything for the password, but it is polite to type your e-mail
address.
Many of the
FTP sites are very busy and you might see the following message
530 Too many users connected currently, please try again
later.
Try again
later. As you use ftp, you will notice that all of the responses from the FTP server
are preceded by an identification number.
You can ignore these numbers. Once you have logged onto an FTP server,
you will need to navigate around the file system. One of the first commands you should enter is help or ? (Fig. 6.13). This will give you a list of available
commands on the FTP server. Table 6.1
describes many of the commonly used commands.
-VE> ftp ftp.jaring.my
220 pop.jaring.my FTP server (Version 2.1aWU(6) Wed
Dec 7 18:22:15 MYT
Connected to pop.jaring.my.
Name (FTP.JARING.MY:wsummers): anonymous
331 Guest login ok, send your complete e-mail address
as password.
Password:
230-
Welcome to FTP server on Jaring Network, Malaysia
230-
230-
Local time is Sat Jun 17 00:00:36 1995.
230-
230-Dear Guest from venus.nmhu.edu,
230-
230-This FTP server is still experimental.
230-
230-The main purpose of this machine is to serve as a
local distribution
230-point for publicly available software and data,
gathered from other
230-servers worldwide. To conserve bandwidth, users from outside Malaysia
230-should not use this machine to pick up data which
originated from other
230-foreign sources.
Please get them from other servers nearer to you.
230-
230-All transactions are logged. If you don't like it, please log off.
230-
230-Uploading is allowed into /pub/incoming directory
on FTP.JARING.MY only.
230-We will move it to /pub/share if you let us know
by e-mail (noc@jaring.my).
230-Give us a short description of the package.
230-*** IF WE DON'T RECEIVE ANY NOTIFICATION, THE FILE
WILL BE DELETED ***.
230-
230-===================================================
230- Please use
ftp.jaring.my rather than jaring.my.
230-===================================================
230-
230-Thank you for your cooperation.
230-
230 Guest login ok, access restrictions apply.
FTP>
Fig. 6.12 - Using ftp
to connect to ftp.jaring.my
Fig. 6.13 - List of ftp commands
? / help Displays ftp commands
ascii Specifies
that files are to be transferred as ASCII files
binary Specifies
that files are to be transferred as binary files
bye / quit Closes
the current connection and returns you to your computer
cd remote
directory Changes the
directory on the remote computer
cdup Same
as cd ..
close Closes
the current connection and returns you to the FTP prompt
dir Lists
the long contents of the directory, similar to UNIX command ls -l
get remote file Copies the named file from
the remote host and stores it on the local host with the same file name
hash Causes
a # to appear for each block of transferred data
lcd local
directory Changes the
directory on your local computer
put local file Copies the named file
from the local host and stores it on the remote host
pwd Tells
you the name of the current directory on the remote host
Table 6.1 - Description of ftp selected commands
One of your
first tasks is to determine where you are and where you can go in the remote
computer's directory structure. You
might start with dir, which gives
you a list of the subdirectories (Fig. 6.14). This usually gives you more
information than you need. The names of
the subdirectories and files are the last column. Different computer systems have different ways of organizing
their files, but most archives are similar to the examples shown. If all you
are interested in are the directory and file names, you can type ls (Fig. 6.15). The command you might
next want to use is cd, to change to
a subdirectory containing the file(s) that you are interested in (Fig.
6.15). If you lose track of where you
are in the file structure of the remote computer, you can type pwd to display the name of the current directory.
FTP> dir
200 PORT command successful.
150 Opening ASCII mode data connection for /bin/ls.
total 22
drwxr-xr-x 6
noc noc 512 May 23 16:50 .
drwxr-xr-x 6
noc noc 512 May 23 16:50 ..
lrwxrwxrwx 1
root other 7 Nov 26 1994 bin
-> usr/bin
d--x--x--x 2
root other 512 Nov 26 1994 dev
d--x--x--x 3
root other 512 Dec 1 1994 etc
drwxrwxr-x 31
noc noc 1024 Jun 16 09:05 pub
d--x--x--x 4
root other 512 Nov 26 1994 usr
226 Transfer complete.
492 bytes received in 00:00:00.89 seconds
FTP>
Fig. 6.14 - Using the dir command
FTP> cd pub
250-Please read the file README
250- it was
last modified on Sat Dec 3 22:31:03
1994 - 196 days ago
250 CWD command successful.
FTP> ls
200 PORT command successful.
150 Opening ASCII mode data connection for file list.
msdos
README
pcdos
.cshrc
info
.kermrc
list.txt
pub
usenet
jalinan
incoming
simtel
archives
list.Z
jaring
cica
budget95
internet
tmp
226 Transfer complete.
289 bytes received in 00:00:00.22 seconds
FTP>
Fig. 6.15 - Using the cd and ls commands
Once you have
located the file(s) that you want to download, you can use the get command. If the file is a text file, you would use the default setting of ascii to retrieve it. However, if you are downloading programs or
utilities, you will need to specify the binary
setting before using the get
command. Since many of the files you
download can be quite long and take a long time to download, you might want to
issue the hash command before the get command. This will allow you to monitor the progress of the file retrieval
(Fig. 6.16).
FTP> binary
226 Transfer complete.
FTP> hash
Hash mark printing on (1024/hash mark).
FTP> get list.Z
200 PORT command successful.
150 Opening BINARY mode data connection for list.Z
(434072 bytes).
##############################################################################
###############################################################
226 Transfer complete.
local: LIST.Z
remote: list.Z
434072 bytes received in 00:02:18.18 seconds
FTP>
Fig. 6.16 – “getting” a file
Usually, files
are grouped together in a compressed file to minimize the amount of data
transfer. The most common archival and
compression file formats are "tar" and "zip". Tar archives a collection of files appended
together and can be unpacked by running the UNIX command tar. Zip files can be unpacked and decompressed using unzip or
PKUnzip. Table 6.2 lists many of the
common file types you will find along with whether to download them using
binary or ascii. To get a more complete
list of file compression and archiving methods for a wide variety of computers,
ftp to the following site and
retrieve the file there.
ftp.cso.uiuc.edu directory: /doc/pcnet/compression
6.6 How to Find Files?
Finding a file
on the Internet using ftp can be quite overwhelming. Certainly you can browse each site and
traverse all of the subdirectories, but not if you have other things to
do. Fortunately, there is a solution
called archie. Archie,
short for archives, is a database system that keeps a list of files on
different FTP sites.
You can use archie in several ways. If your computer has the archie client installed, you can simply
run it from there by typing archie. You can also use e-mail to an archie server requesting the locations
of files. The third method is to telnet
to an archie server and use it there
(Fig. 6.17). Table 6.3 lists several
sites maintaining archie servers.
You can send mail to many of these sites at 'archie@site_name' for a help file.
Log onto these any of these servers using "archie" as the login name
and press the "Enter" key for the password.
.arc bin ARChive (hardly used anymore)
.arj bin
Arj (mostly MS-DOS)
.au bin Audio sound files
.gif bin Graphics Interchange Format
.gz bin GNU Zip
.hqx asc HQX (Mac, Mac
equivalent of uuencode)
.jpg bin JPEG (graphics
format)
.lzh bin LHa, LHarc, Larc
.mpg bin MPEG (graphics format)
.shar asc SHell ARchive
(mostly Unix)
.sit bin
Stuff-It (Mac)
.tar bin Tape ARchive (mostly Unix)
.txt asc Text File
.uu asc uuencode/uudecode
(also .uue)
.wav bin Wave sound files
.Z bin compress (mostly Unix, seen in combination
with tar as .tar.Z files)
.zip bin Zip (either PKZip or Zip/Unzip)
.zoo bin Zoo
Table 6.2 - Common file types found on FTP servers
To find a file
called 'filename' you would type: archie
filename if you are using a client or prog
filename (Fig. 6.18) if you are logged onto an archie server. There are lots of options available, so you will
probably want to use help. Once you
have entered the command, sit back and wait.
Archie servers are generally
very busy and it may take quite a while to locate all of the files you are
interested in. Most servers will give
you an estimate of how long it will take and how far down the queue you are on
that server. Be patient and be willing to try another server.
Fig. 6.17 - Atelneting@ to an archie server
domain name IP address country
archie.au 139.130.4.6 Australia
archie.th-darmstadt.de 130.83.22.60 Germany
archie.wide.ad.jp 133.4.3.6 Japan
archie.kr 128.134.1.1 Korea
archie.sogang.ac.kr 163.239.1.11 Korea
archie.luth.se 130.240.18.4 Sweden
archie.switch.ch 130.59.1.40 Switzerland
archie.ncu.edu.tw 140.115.19.24 Taiwan
archie.doc.ic.ac.uk 146.169.2.10 United
Kingdom
archie.unl.edu 129.93.1.14 USA
archie.internic.net 198.48.45.10 USA
archie.rutgers.edu 128.6.18.15 USA
archie.ans.net 147.225.1.10 USA
archie.sura.net 128.167.254.179 USA
Table 6.3 - List of archie servers
Fig. 6.18 - Finding files about Kuala Lumpur
6.7 FTP
and Archie Software
There are
several very good software packages for Windows and Macintosh users. These are available from most of the popular
ftp archive sites listed in the next
section.
Windows users
might look for WS_FTP32, FTP, WinQVT and WSArchie. All of these are available in sites listed in the next
section. Once you have downloaded the
ZIP file and "unzipped" it, you will need to create a program icon
and install the program as a Windows application. To activate the program, simply click on the icon (Fig. 6.19).
Fig. 6.19 - FTP icons
Once you've
clicked on the FTP icon (Fig. 6.20), you will see the ftp prompt. You will need
to open the site of the FTP server
and then you can issue any of the ftp
commands. Don't forget to type bye when you are finished so that your
computer will be disconnected from the remote server.
Fig. 6.20 - FTP client
6.8 Where to Go From Here
The best way
to learn how to use these Internet tools, is to experiment with them. The following are lists of interesting telnet and ftp sites for you to explore.
As you explore one, you will find many more to explore from there.
hermes.merit.edu
directory
of remote services (type HELP at prompt)
martini.eecs.umich.edu 3000 (martini) Geographic Name Server
books.com BBS
bookstore
career.com BBS
career service
freenet-in-a.cwru.edu Cleveland
Free-Net BBS
tudrwa.tudelft.nl Delft
University BBS (log-in as bbs)
heartland.bradley.edu Heartland
Freenet BBS (log-in as bbsguest)
Table 6.4 - Telnet Locations
ftp.jaring.my Malaysian
ftp site
ftp.cica.indiana.edu Windows archive
sumex-aim.stanford.edu Macintosh archive
wuarchive.wustl.edu &
oak.oakland.edu
DOS
& Amiga archives
ftp.rpi.edu
Internet
& Computer-Mediated Communications
(AKA
The December List)
csd4.csd.uwm.edu
Special
Internet Connections (Scott Yanoff s List)
ftp.cs.wisc.edu
Landweber's
list of connected countries
rtfm.mit.edu
archive
of USENET newsgroups
ftp.netcom.com/pub/mailcom/internaut on-line
magazine
boombox.micro.umn.edu University
of Minnesota's ftp site
sunsite.unc.edu University
of North Carolina's ftp site
ftp.iij.ad.jp Tokyo
tricera.nmhu.edu New
Mexico Highlands University
ftp.borland.com Borland
ftp.microsoft.com Microsoft
ftp.novell.com Novell
ftp.netcom.com SlipKnot
ftp.NCSA.uiuc.edu Mosaic
Web
ukanix.cc.ukans.edu Lynx
ftp.utas.edu.au Trumpet
News Reader
ftp.mcom.com Netscape
titan.ksc.nasa.gov NASA
rtfm.mit.edu Compression
FAQ & ftp lists
cs.ucr.edu Computer
Viruses archive
