Telnet is a both a network protocol and an application that uses that protocol. Most often, telnet is used to connect to remote computers and issue commands on those computers. It's like a remote control for the internet!
Telnet is used for a variety of reasons. Almost all of them involve telneting to a remote device and issuing commands. Here are some examples:
Servers and networked devices may run a telnet server application, often called a service or daemon. This service allows for telnet clients to connect to them and issue commands. It's important to understand that if you want to telnet to some host, it must be running such a service.
If you would like to try out telnet, check out our list if interesting places to see:
The computer to which you wish to telnet must be running a telnet server application. Additionally, all firewalls between the two computers must allow access to telnet (usually on port 23). Most personal computers and workstations are not running telnet services, so you'll need to find a telnet server and install it if you want to telnet to that computer.
Basic telnet includes no encryption of traffic and is therefore susceptible to eavesdropping (aka packet sniffing). In most remote access situations, telnet has been replaced by ssh for improved security across untrusted networks. However, telnet continues to be used for remote access to fun services such as MUDs and talkers, remote access on internal trusted networks, and it remains a solid network troubleshooting tool as well.
Check out our page about Telnet Applications.
If you're certain you understand the security implications, read on. Otherwise, you might be better off looking in to the various Windows remote access options and services.
Microsoft makes this knowledge base document available for installing and enabling the telnet service on Windows. It covers a variety of Windows versions:
If you're certain you understand the security implications, read on. Otherwise, you might be better off looking in to an ssh server.
Most unix like operating systems make a telnet server/daemon available. Check the man pages and your operating system documentation for more details. Below are a couple of examples for installing telnetd:
Telnet applications are useful for testing remote services such as web services or smtp mail servers. You just need to telnet to the appropriate ip and port, and know how to issue commands for the relevant protocol such as HTTP or SMTP.
As an example, you can use telnet to request a web page from a remote server with just a couple of commands:
Here's an example for telneting to google.com and requesting the index page:
[rain ~]$telnet google.com 80 Trying 188.8.131.52... Connected to google.com. Escape character is '^]'. GET / HTTP/1.0 200 OK Date: Mon, 30 Sep 2013 02:21:47 GMT Expires: -1 Cache-Control: private, max-age=0 Content-Type: text/html; charset=ISO-8859-1 --snip-remaining-output-- Connection closed by foreign host.
You can find more good information on telnet at wikipedia.
Microsoft also has a Windows oriented telnet faq @ http://windows.microsoft.com/en-us/windows-vista/telnet-frequently-asked-questions.
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