Simple test if TCP port is open

Note: This post is 6 years old. Some information may no longer be correct or even relevant. Please, keep this in mind while reading.

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 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.