title: example to explain unix domain socket - AF_INET vs AF_UNIX
body: <p>while I was reading for what <code>AF_INET</code> means, I learned that there is another family called <code>UNIX domain socket</code>. Here is the <a href="http://en.wikipedia.org/wiki/Unix_domain_socket" rel="noreferrer">wiki link</a> I read about this. </p>
  
  <p>I do not understand what this means:</p>
  
  <blockquote>
    <p>Unix domain sockets use the file system as their address name space.
    They are referenced by processes as inodes in the file system. This
    allows two processes to open the same socket in order to communicate.
    However, communication occurs entirely within the operating system
    kernel.</p>
  </blockquote>
  
  <p>If I want to do <code>SSH or FTP</code>, what family do I use <code>AF_INET or AF_UNIX</code>. I am actually confused here a bit.</p>