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Lack of Telnet Client in Windows Vista

For the most part I will try to limit the number of “rants” on this Blog, but I have one I feel the need to share today (and I will even throw in a bit of helpful troublshooting advice).

Who in the world decided that removing the telnet *client* (not SERVER) from Windows Vista was a good idea?  As a network engineer I want to hunt that guy/gal down and give them a piece of my mind!  For crying out loud it is a 202KB executable file!

I could fully understand if we were talking about a *service* that had to load and run at boot that could represent a remote compromise opportunity, but no, we are talking about an extremely simple application that can simply open up a TCP connection to a remote host.

Windows Telnet Size

Windows Telnet Size

The worst part is that to install the Telnet client after the fact requires a number of clicks to drill down to wherever they hid the “Add/Remove Programs” control panel and then once you find and check the telnet client it takes like 20 minutes to install this 202KB file!

The reason this frustrates me so much is that if I am on a machine and I need to prove that I have TCP connectivity to something, the best way to do this is to simply type “telnet <ip or host> <port>” and hit enter.  I will immediately know if the remote host sent back a RST (connection denied), or if it connected (command terminal often will just be blank or the server could prompt something), or if it times out then the packets are getting lost somewhere.

Telnet Plunger Port 22

Telnet Plunger Port 22

Here you can see the result of the command above.  The connection opened successfully (as evidenced by the prompt clearing), and in this case SSH prompted the client with it’s version number.  You can press “ctrl-]” to drop to the telnet shell and enter “quit” to exit.

Telnet SSH Response

Telnet SSH Response

I use this extremely frequently when there is an access control list or firewall in the way that does not allow ICMP packets, or if I need to check if a port is open.  Also, I use this to prove “it’s not the network” when users complain of application issues and blame the network.  If I can open a TCP connection to their application server then that proves that round trip data flows between the devices are working.

-Eric

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  1. March 24th, 2009 at 09:02 | #1

    Putty on a USB drive? Not as convenient, I know, but it’ll do the trick.

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