12-Jul-2018
When macOS High Sierra (10.13) was released, the
telnet utility disappeared. This has probably been a good move by Apple since
telnet is outdated and not a secure protocol; it shouldn't be used in general. However,
telnet did serve a useful function - checking if it was possible to connect to a remote server on a particular port. Luckily there is a much better tool for this included in macOS -
nc (netcat).
Using
nc is simple and it has command line arguments that are very similar to
telnet. I like to use the
-vz arguments whenever I need to check if a remote server can be reached on a particular port. These arguments make
nc have this behaviour...
-v Have nc give more verbose output.
-z Specifies that nc should just scan for listening daemons, without sending any data to them.
The result is
nc tries to connect to the server and then immediately terminates if it succeeds. Here's an example...
If a connection cannot be established and a timeout is reached the output is like this (timeout can be controlled via the -G option i.e.
-G 5)...
If a connection is refused, the output is like this...
-i
A quick disclaimer...
Although I put in a great effort into researching all the topics I cover, mistakes can happen.
If you spot something out of place, please do let me know.
All content and opinions expressed on this Blog are my own and do not represent the opinions of my employer (Oracle).
Use of any information contained in this blog post/article is subject to
this disclaimer.
Igor Kromin
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