How to close the port for external ip in ubuntu (and how to open it)?

Question

ubuntu

Good afternoon!
Can you tell me methods to close the port for external connections in ubuntu? At the same time, applications from localhost must have access to this port. And how to open back the port,

Answer 1

The best thing is to listen on the port only on 127.0.0.1, how to do this depends on the program settings. Well, or through iptables close the port from the outside.