title: Where to start learning about Android Vpn?
body: <p>Looking around the Android API, I noticed the VpnService.  I thought it was pretty cool and I wanted to learn about it to see what kind of apps would be possible with it, so I started looking around for tutorials and explanations.</p>
  
  <p>I discovered that I know <em>nothing</em> about what the different methods are for, why they work, or how to manipulate them. Words and phrases like TCP/UDP, network interface, TUN, and handshake popped out at me, but overall, I have no idea how these things actually work or how to use them.  Could I get a point in the right direction to maybe a book or website where I could learn the basics about this stuff and work my way up to the more advanced things like Android Vpn?</p>