using the “telnet” utility for testing ports – it’s sort of gone (on Windows nowadays), but they allow you to re-enable it

Back in the old days before SSH was “the standard way” to log into a remote computer, there “were” a protocol (and a utility) called “telnet” in order to achieve that.

But the “telnet” utility traditionally also served for testing deliberate TCP/IP ports somewhere in the Internet resp. on your “Intranet”, e.g.

Can I connect to that Oracle DB server on that specific port?

That’s particularly useful, because the applications themselves (whether GUIs or CLI utilities) usually have poor ways of dealing with facts like:

• some firewall prevents you from accessing that Oracle DB server
• there is simply no route to that Oracle DB server

The “telnet” utility does not really have nicer error messages, but “everybody knows”, what it means, if you tell them, you tried to “telnet HOST PORT“, and it failed or timed out. And you know, it’s not the application, but it’s the network or the server.

In  recent versions of Microsoft Windows the “telnet” utility got made sort of invisible, but there is an easy way to make it visible and available. See the links below!

But if you already have the PuTTY suite of utilities available on your PC, maybe you prefer the “plink” utility:

• https://the.earth.li/~sgtatham/putty/0.67/htmldoc/Chapter7.html#plink-usage

% …plink -telnet -P port host

• http://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html – where to find the PuTTY suite of utilities

The Windows “defect”  and its fix:

• http://superuser.com/questions/349080/is-there-a-telnet-utility-for-windows
• http://superuser.com/questions/110760/why-isnt-telnet-enabled-by-default-in-windows-7
• http://www.webtlk.com/2009/07/24/how-to-enable-telnet-in-windows-vista-and-windows-7/

If you wish to turn on and enable the “telnet” utility, here is what to do:

1. Click Start.
2. Click Control Panel.
3. Now, go to Programs or Programs and Features.
4. Click Turn Windows features on or off. (only “administrators” can proceed here.)
5. In the Windows Features dialog box, tick Telnet Client check box.
6. Click OK.