                               TELNET (PART ONE)
   
We are about to enter a new section of this workshop. For the past week, we have 
talked about communicating on a one-to-one basis (e-mail) and on a one-to-many 
basis (LISTSERV and Usenet). 
Today, I'm going to show you how to log in to other computers around the world 
and take full advantage of the public programs and services that these other 
computers offer. 
There is some bad news, though. Some of you, especially a good number of you 
with "level one" Internet access, do not have access to TELNET. If this is true 
for you, please accept my apologies. I promise to make it up to you next week 
when I show you File Transfer Protocol -- and besides, you can always take 
today's lesson and tomorrow's lesson and bug your local Internet provider into 
offering TELNET (you can also save this lesson for the day that you do have 
TELNET access). 
With TELNET, the commands that you type on your keyboard are sent from your 
terminal to your local Internet service provider, and then from your provider to 
the remote computer that you have accessed. Unlike the LISTSERV commands that 
you sent last week that took CENTURIES to process (okay, a *slight* 
exaggeration), TELNET commands (usually) travel so fast that you can't even tell 
that you are using a remote computer. 
So what can you do with this ability to log into remote computers? If your local 
Internet provider allows it, it is possible for you to TELNET into your account 
from another city and check your e-mail while you are on vacation or away on 
business. You can also TELNET into huge databases to do research, or even TELNET 
into libraries around the world to check if they have a certain book that you 
are looking for. TELNET also offers an easy entry into the world of Gophers and 
the World Wide Web for those people who may not otherwise have access to these 
tools. 
Last Tuesday (in MAP04: E-MAIL), I showed you that an Internet address for a 
user looked something like: user@address. Well, since we are no longer 
interested in the person -- we want to access the computer, not the person -- we 
can throw away both the "user" and the "@" part. All we care about now is the 
stuff *after* the @. 
TELNET addresses look something like this:


     seabass.st.usm.edu        cybernet.cse.fau.edu
     bbhost.hq.eso.org         fedworld.gov
     128.118.36.5              192.160.13.1
Gee ... that's easy. Also notice that TELNET addresses can be in domain name 
format (i.e. seabass.st.usm.edu) or in IP address format (i.e. 120.118.36.5). 
(Note: both the domain name system and the IP address system were discussed in 
MAP04: E-MAIL). 
You may also see TELNET addresses with numbers stuck on the END of them. Those 
numbers are "port" numbers. Port numbers don't have anything to do with hardware 
ports on the computer; instead they are (sort of) a way for you to tell the 
remote computer which program or server you want it to pull up. A TELNET address 
with a port number allows you not only to access a remote computer, but to also 
pull up a specific program or server on that remote computer (BTW, the standard 
port number is port 23):


     seabass.st.usm.edu 23     cybernet.cse.fau.edu 2010
     bbhost.hq.eso.org 6969    fedworld.gov 4242
     128.118.36.5 23           192.160.13.1 66
We seem to have the addresses down pat. Now for the fun stuff! 
There are seven steps to a successful TELNET session. These steps are all based 
on simple common sense, and I will explain them all in a minute. But first, here 
are the seven steps: 
    Start-up the TELNET program 
    Give the TELNET program an address to connect to (BTW, some really nifty 
    TELNET packages allow you to combine steps 1 and 2 into one simple step!) 
    Make a note of what the "escape character" is 
    Log in to the remote computer 
    Set the "terminal emulation" 
    Play around on the remote computer 
    Quit 
Now let's talk about each of these steps. There are a lot of different TELNET 
software programs around, but each of these programs operate on the same basic 
principles. (BTW, my explanation may be a little "mainframe-y" but you will soon 
discover that you can easily translate my explanation so that you can use TELNET 
in Windows or on a Macintosh). 
Starting the TELNET program is easy. All most of you have to do is type the word 
TELNET on your command line, and the program will start right up. If you are 
using Windows or a Macintosh (or an equivalent), double-click on the TELNET 
icon. 
The second step is to give the TELNET program the address of the computer that 
you want to access. This is where the programs start to differ. Some programs 
will automatically ask you to enter the address of the remote host, but most 
won't. If your program does not automatically ask you for the address, you need 
to type

open <site address> <port number>

on the command line. For example, to get TELNET access to YALEINFO.YALE.EDU 
7000, you would type OPEN YALEINFO.YALE.EDU 7000. (If you are using Windows or a 
Mac, the OPEN command may be located on a pull-down menu). If you don't include 
the port number, TELNET will automatically assume that you want to connect to 
port 23. 
Remember when I said that some nifty TELNET programs allow you start-up the 
TELNET program and access the address all in one easy step? Instead of doing the 
two steps I just went over, you may be able to just type

telnet <site address> <port number>

on the command line (for example: TELNET YALEINFO.YALE.EDU 7000). 
After you have told TELNET which computer you want it to access, and right 
before you gain access to the remote computer's login screen, you will see 
something like this:

telnet YALEINFO.YALE.EDU 7000
Trying 130.132.21.53 Port 7000 ...
Connected to YALEINFO.YALE.EDU
Escape character is ...

This tells you that your TELNET program is trying to access the 
YALEINFO.YALE.EDU 7000 address, gives the IP address for YALEINFO (remember 
those from MAP04?), tells you when you are connected, and gives you the escape 
character. REMEMBER THE ESCAPE CHARACTER! You are going to need it in a second 
:) 
The next step is to log in to the remote computer. Everyone should know how to 
log in to a computer by now ;) <=== a winking smiley 
If you are accessing a public site, the "login" -- the "password" that you need 
to access the remote computer -- will probably be publicly known. For example, 
tomorrow I will send you a list of several dozen TELNET sites, including their 
addresses and logins. Some public sites even TELL you what the login is when you 
TELNET to them! Heck, some TELNET sites are wide open and do not require a login 
or password at all!! 
The fifth step is to set the terminal emulation. All this means is that you are 
going to tell the remote site how data should be shown on your screen. The most 
common terminal emulation setting is VT100, which is the standard for 
terminal-based communications. 
If you do not have a VT100 terminal, or a terminal that can pretend its a VT100 
terminal. you may have to set your terminal emulation to either your correct 
terminal type or, if you do not know your your correct terminal type, to a 
"dumb" terminal emulation. 
Fortunately, some TELNET sites automatically take care setting the terminal 
emulation for you, so you don't even have to worry about it. 
If you end up with a screen full of gibberish, chances are you did not use the 
correct terminal emulation setting. Your best bet if this happens is to 
disconnect from the site and try again. 
I think you can figure out the sixth step -- play around on the remote computer 
-- all by yourself :) 
The final step is to quit. Some sites are nice and tell you how to do this, but 
most expect you to figure out how to quit on your own. That is where the escape 
character comes in! 
Remember that once you access the remote computer, every keystroke of yours will 
be carried out not on your computer but on the remote computer! Typing the 
escape character (usually the control key and the right bracket key pressed at 
the same time) temporarily interrupts your TELNET session and puts you into the 
TELNET command mode. 
Once you are in the command mode, you can use a couple of commands: 
    CLOSE 
    Closes your TELNET connection to the remote computer and either returns you 
    to the command mode (if you started in the command mode) or quits TELNET. 
    QUIT 
    Quits the TELNET program; if you are connected to a remote computer, QUIT 
    will disconnect you from the remote computer and then quit TELNET. 
    SET ECHO 
    If you can't see what you are typing, or if you type and see double, this 
    command should take care of the problem 
    <ENTER> (or <RETURN>) 
    Pressing the enter or return key will take you out of TELNET command mode 
    and return you to your TELNET session. 
    OPEN 
    Opens a connection to a remote computer 
So, if you are in the middle of a TELNET session and you decide to quit, you 
would type the escape character to enter the TELNET command mode, and then type 
the word QUIT. 
One last thing and I will let you go: regular TELNET does not work if you are 
trying to TELNET to an IBM 3270 mainframe computer. You'll have to use TN3270 
instead. It works just like TELNET, only the keys on your keyboard may change a 
little (IBM uses something called map3270 to lay out the keys, and IBM uses a 
lot of function keys). 
