title: Linux open ports manually and valid reasons to do it
body: <p>How open a port manually?</p>
  
  <p>I know that if I install apache opens port 80, ssh opens port 22 and that I can change port number in your configuration files.</p>
  
  <p>I was listening to people talk about open ports manually.</p>
  
  <p>How can I make this process? When should I do it?</p>
  
  <p>Thank you.</p>