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<td width="80%" align="center" valign="bottom">Chapter 13 Basic Network Commands</td>
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<h1 class="SECT1"><a id="BASIC-NETWORK-COMMANDS-TELNET"
name="BASIC-NETWORK-COMMANDS-TELNET">13.5 <tt class="COMMAND">telnet</tt></a></h1>
<p>Someone once stated that <tt class="COMMAND">telnet</tt>(1) was the coolest thing he
had ever seen on computers. The ability to remotely log in and do stuff on another
computer is what separates Unix and Unix-like operating systems from other operating
systems.</p>
<p><tt class="COMMAND">telnet</tt> allows you to log in to a computer, just as if you
were sitting at the terminal. Once your username and password are verified, you are given
a shell prompt. From here, you can do anything requiring a text console. Compose email,
read newsgroups, move files around, and so on. If you are running X and you <tt
class="COMMAND">telnet</tt> to another machine, you can run X programs on the remote
computer and display them on yours.</p>
<p>To login to a remote machine, use this syntax:</p>
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">telnet <<var
class="REPLACEABLE">hostname</var>></kbd>
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<p>If the host responds, you will receive a login prompt. Give it your username and
password. That's it. You are now at a shell. To quit your telnet session, use either the
<tt class="COMMAND">exit</tt> command or the <tt class="COMMAND">logout</tt> command.</p>
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<p><tt class="COMMAND">telnet</tt> does not encrypt the information it sends. Everything
is sent in plain text, even passwords. It is not advisable to use <tt
class="COMMAND">telnet</tt> over the Internet. Instead, consider the <tt
class="COMMAND">Secure Shell</tt>. It encrypts all traffic and is available for free.</p>
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<h2 class="SECT2"><a id="AEN4593" name="AEN4593">13.5.1 The other use of telnet</a></h2>
<p>Now that we have convinced you not to use the telnet protocol anymore to log into a
remote machine, we'll show you a couple of useful ways to use <tt
class="COMMAND">telnet</tt>.</p>
<p>You can also use the <tt class="COMMAND">telnet</tt> command to connect to a host on a
certain port.</p>
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">telnet <<var
class="REPLACEABLE">hostname</var>> [port]</kbd>
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<p>This can be quite handy when you quickly need to test a certain service, and you need
full control over the commands, and you need to see what exactly is going on. You can
interactively test or use an SMTP server, a POP3 server, an HTTP server, etc. this
way.</p>
<p>In the next figure you'll see how you can <tt class="COMMAND">telnet</tt> to a HTTP
server on port 80, and get some basic information from it.</p>
<div class="FIGURE"><a id="FIG-BASIC-NETWORK-COMMANDS-TELNET-WEB"
name="FIG-BASIC-NETWORK-COMMANDS-TELNET-WEB"></a>
<p><b>Figure 13-1. Telnetting to a webserver</b></p>
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">telnet store.slackware.com 80</kbd>
Trying 69.50.233.153...
Connected to store.slackware.com.
Escape character is '^]'.
HEAD / HTTP/1.0
HTTP/1.1 200 OK
Date: Mon, 25 Apr 2005 20:47:01 GMT
Server: Apache/1.3.33 (Unix) mod_ssl/2.8.22 OpenSSL/0.9.7d
Last-Modified: Fri, 18 Apr 2003 10:58:54 GMT
ETag: "193424-c0-3e9fda6e"
Accept-Ranges: bytes
Content-Length: 192
Connection: close
Content-Type: text/html
Connection closed by foreign host.
<samp class="PROMPT">%</samp>
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<p>You can do the same for other plain-text protocols, as long as you know what port to
connect to, and what the commands are.</p>
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