This question already has an answer here:

I am running a web server on a machine with Ubuntu 11. Everything is accessible from the local network, but not from outside. What can I do to check to make sure the appropriate ports are open?

I am relatively new to Ubuntu and server management, so any "dumbing down" is just fine.

Appreciate any help. Google search hasn't given me much actionable advice.

merged by Seth Aug 14 '17 at 20:17

This question was merged with How can I see what ports are open on my machine? because it is an exact duplicate of that question.

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