V. Terminal Emulation

1. Prerequisites: 
* Have an account on any remote computer system or you know 	
the public userid/(password)
* You know its internet domain address and/or you can connect by 	
phone to it by modem

2. How:
* Run a special program called telnet on your computer (or on a 	
remote computer).
* This program uses the internet to connect to the computer of 	
your choice.
* Once connected, telnet acts as an intermediary between your 	
computer and the remote one.
* Your keyboard and screen or window seem to be directly 	
connected to the remote system.

3. Port Numbers
* A port in UNIX is a connection between 2 devices or systems.
* The default port number for telnet commands is 23
* A host can support many connections to a specific port at the 	
same time (e.g. 100 concurrent users on 	downwind.sprl.umich.edu 	(Weather Underground)
* To get a successful connection, a program, must be listening 	
(waiting) on that port
* Internet systems use different ports to offer different, special 	
services

5. telnet commands
	?			Display (print) this help information
	close			close current connection to the remote 
					machine
	display		display operating parameters for this session
	mode		try to enter line-by-line or character-at-a-					time mode
	open <host>	connect to a remote computer site
	quit			exit telnet program
	send <parameter> transmit special characters ('send ?' for 
					more)
	set			set operating parameters ('set ?' for more)
	status		display (print) status information
	toggle		toggle operating parameters ('toggle ?' for 
					more)
	^] 			(<CTRL-]>) suspend remote computer 
					activity, get a telnet prompt
	z 			suspend telnet program, get a UNIX shell 
					prompt

6. telnet hints:
* the telnet message "unknown host" can be caused by: computer 	
address spelled wrong or the remote computer is temporarily 	
unavailable or you specified the name of a computer that is 	
not on the internet.
* the telnet message "Connection refused" can be caused by an 	
improperly functioning system or a saturated system which 	
cannot accomodate another telnet session.
* the telnet message "Connection dropped" can be caused by a 	
problem with your network or the remote computer system 	
(e.g. that system crashed).  Start over in a few minutes to 	
(re)connect.
* Before closing a connection or quitting telnet, log out from the 	
remote computer
* Type man telnet when on unix systems for online documentation 	
about telnet
* Many Remote hosts automatically log you out if there is no 	
activity for a time (e.g. 15 minutes).  Remember this if you 	
suspend a telnet session (via a z); you may be disconnected.

Questions? Robert Katz: katz@ned.highline.edu
Last Update August 8, 1998