src/kits/network/libnet
This shared library is the way BeOS R5 provide the sockets POSIX/BSD API to apps. Being binary compatible with R5 make this library implementation tedious.
src/kits/network/libnetapi
This shared library contains thin C++ classes wrapping the C sockets POSIX/BSD API into these BNet* classes we're used under BeOS: look at them in your BeBook