title: IPPROTO_IP vs IPPROTO_TCP/IPPROTO_UDP
body: <p>I'm having some trouble finding documentation on what the distinction between these settings for the third argument to <code>socket</code> is. I know about TCP and UDP and their differences and also that IP is one layer up (down?) on the stack... My UDP code seems to work the same whether I set it to <code>IPPROTO_IP</code> or <code>IPPROTO_UDP</code>. </p>