Your guide was what everyone else recommended when I was stumbling around learning networking a couple years back (reversing and reimplementing an iOS framework that used the BSD sockets API–not really the best environment for someone who couldn't tell connect(2) from accept(2)). With your help I was able to get through that and the understanding carried me through college, in some networking classes that were decidably less educational or useful than your writing. Not bad for a document bearing a copyright from years before I was born!