Using telnet to verify port availability

As you probably know, Telnet is network protocol, primary used for establishing terminal connections to devices. Telnet as protocol is highly insecure and I strongly recommend not to use it for device administration, but there is one functionality you can use with no fear. You can use Telnet to verify port availability on servers or workstations.

Just to be clear, you can verify port availability only for TCP port, regarding fact that TCP is connection oriented while UDP is not. One more thing: we can say that Telnet is universal `tool`and you can use it on Windows as well as on Linux distros.

So, imagine you want to verify if HTTPS port is opened on some server.

Generally syntax goes like this: telnet host port(tcp)

Start Terminal on Linux or Command Prompt on Windows and type following:

ittutorials@ubuntu:~$ telnet gmail.com 443
Trying 216.58.209.197…
Connected to gmail.com.
Escape character is ‘^]’.

I checked GMAIL service to reproduce situation and received answer from server that I am connected. Of course you can use IP address instead domain name. But if you try to verify TCP port 1521 (Oracle) you will receive message telnet: Unable to connect to remote host: Network is unreachable meaning that port is no available.

One more thing: there are some additional settings in Windows 7 and above regarding telnet client installation that you ha to perform. Tutorial is on our site and you are welcome to use it.

That`s it, keep an eye on www.it-tutorials.net as we will continue with more tutorials . On our website you will find a lot of tips and tricks for any IT field !

 

 

 

 

Dejan Dzodan

Dejan Dzodan

IT professional for more then 15 years, mostly in financial institutions but with experience in ISP and retail. Proven in networking and overall infrastructure projects. Cisco instructor.

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