I'll bet you've occasionally heard the word "telnet" mentioned as
you've surfed the net. And I'll also bet that, like most people, you
really don't have any idea what this strangely named thing is for. Yet
this little known thing is one of the more powerful tools available to a
webmaster.
What is telnet? This is a way to attach directly to a web server to
give it commands. Using Telnet you are not talking through a web browser,
an email client, a newsgroup reader or even an FTP program. In fact, what
you can do with Telnet is log into your account on your server (or your
hosts server) and make it do things that before now you've only dreamed
of.
- What is telnet exactly?
- Telnet is a protocol (a well defined way of communicating) which
allows character oriented communications between a client (you) and a
computer system (the machine hosting your web site). Telnet basically
makes the computer believe that your computer is an
ASCII (character based) terminal.
- Why is Telnet useful?
- Using Telnet you log directly into the server and feed it commands.
This usually applies to Unix-style systems, although in theory it works
as well on Windows NT and Windows 2000 hosts (usually Telnet is disabled
on those kinds of operating systems due to severe security risks).
- How do you get Telnet?
- There are two parts to Telnet. First, you need to contact your web
host and find out if they support Telnet access to your account. If you
pay for your hosting and they run a Unix-style box, then it's very
likely that you will be granted Telnet access.
Once your host has granted you access, you will need to get a Telnet
client. Some operating systems (such as Windows 2000 Professional) come
with one of these clients automatically. Otherwise, you can do a quick
search on Zdnet or Download.com to find a good one.
- What Telnet clients are available?
- There are many dozens, if not hundreds, of Telnet clients available.
Some of them include the following:
- Once you have Telnet access, what can you do?
- If the box is a Unix machine, you can feed to Unix commands. These
are useful for determining the environment, setting up timed jobs, and
performing certain specific maintenance tasks.
- What commands do you need to know?
- Once you've logged into the server, you will need to know and
execute operating system commands. In general, these will be Unix
commands (although VAX and Alpha based web hosts are still around),
although you may occasionally run into a Windows system with Telnet
access (these will need DOS commands).
- What can't you do with Telnet?
- Telnet is not a web server so does not have a clue about web pages.
It is also not an email client (although you may be able to run an email
program from the Telnet session), a newsgroup reader or an FTP program.
- How did Telnet come about?
- Okay, put on your way-back glasses for minute so we can go back in
time. Back in the good old days of computers, everything was done on
huge, high-prices machines called mainframes. To communicate with a
mainframe you used something called a terminal. The main difference
between a terminal and a modern PC is a terminal is very stupid.
Terminals only allow a small set of characters (about 127 different
ones) to be typed and printed. There are no graphics of any kind, and
everything was black and white (no colors). Just characters being typed
and printed from left to right.
Telnet was developed around 1980 by Jan Postel to allow people to
connect to one of these computer systems from a remote location. The
Telnet software pretended it was one of the really dumb terminals.
That's all Telnet is - a way to get to a machine and log in as if one
were typing on a terminal.
- Why don't all web hosts support Telnet?
- Supporting Telnet is more difficult than just running a standard web
host. There are also significant security risks associated with this
protocol which need to be considered.
- Is there a free host which supports Telnet access?
- It's very unlikely that you will find a free host which allows
Telnet access.
- What is the future of Telnet?
- Unix-style servers are very, very popular. Over time, I think, as
better and better tools are developed I think Telnet will fade into the
past. Until then, it's sometimes the old way to get done what you need
to get done.
Unless otherwise noted, all photos and text is Copyright © Richard G Lowe, Jr.
