title: Understanding the process of receiving network packets
body: <p>I started to learn Linux Networking and packets filtering. <a href="http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO-6.html" rel="nofollow">In the iptables documentation</a> it is stated that:</p>
  
  <ol>
  <li>If a packet is destined for this box, the packet passes downwards in the diagram, to the INPUT chain. If it passes this, <strong>any processes waiting for that packet will receive it</strong>.</li>
  </ol>
  
  <p>So, suppose there're 3 server apps on a host. <strong>Servers A and B are TCP servers</strong>, and <strong>C is UDP server</strong>.
  Is it true, that if we receive an UDP packet, <strong>at IP level</strong> this packet is to be delivered for apps A, B, C? Or sockets of apps A &amp; B wouldn't receive this packet at all?</p>