Simple test if TCP port is open
Caveat Lector: This blog post was published 8 years ago. Depending on the content, it may no longer be applicable or relevant.
There are other more complicated tools to achieve the same (like nmap whose manpage makes your head spin), but this is a very simple solution using netcat:
nc -zv 127.0.0.1 80
To programmatically evaluate the result, use the standard Bash $? variable. It will be set to 0 if the port was open, or 1 if the port was closed.
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