Telnet without Telnet

Monday 18 November 2013

Recently I had to verify the connectivity of a new server. So, I logged in over SSH and simply typed

telnet my.server.com 5432

to test the firewall rules. But to my suprise, telnet was not installed on that machine.

So, what now?

Ok, we could check if stuff like curl or wget is installed but this won’t help in every case. If you simply want to know if a certain port is open you can use the command:

exec 3> /dev/tcp/my.server.com/5432;[ $? == "0" ] && echo ok || echo fail

Not as neat as telnet but does the job 🙂

 For related article, read this:

Application Knowledge

When discovering programs languages, designers typically find elements of how these words are executed within calculating systems. This indicates that each time you learn a new language, you learn something more about the effectiveness, performance and style aspects of programs in general. Numerous languages execute their structures in similar ways, so learning about general implementation concepts gives you the knowledge to process with efficiency in mind, whatever language you are utilizing.

Methods

Some programming languages are similar, but some take vastly different techniques to application processing. For instance, object-oriented languages, such as Java, divided application tasks between a set of items with specific obligations. Languages are often categorized as high or low level. The higher level a language is, the more it involves abstraction from calculating hardware. Procedural languages provide the computer system a series of specific directions to perform, whereas functional languages specify application habits using mathematical functions. Understanding about various programming language approaches gives you a wider variety of choices regarding how you approach particular projects yourself.

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