title: struct sockaddr_un vs. sockaddr
body: <p>How is <code>struct sockaddr</code> different from <code>struct sockaddr_un</code> ?</p>
  
  <p>I know that we use these structures in client-server modules, for binding the socket to the socket address. And we use a cast operator for it to accept struct <code>sockaddr_un</code>.</p>
  
  <p>I want to know how different/similar they are, and why the cast operator?</p>