In https://ruby-doc.org/stdlib-2.7.0/libdoc/socket/rdoc/Socket.html#method-c-new, the Ruby terminology for the "family" argument is "socket domain", and the argument accepted is a symbol like :INET instead of traditional constants like AF_INET/PF_INET. https://stackoverflow.com/questions/4965835/network-programming-socket-function-address-family-vs-protocol-family says that protocol and address family constants are in practice interchangeable, despite theoretically being potentially different. To be in line with terminology that Ruby uses for sockets, we should rename our occurrences of "family" to "domain" and use the symbols instead of numeric constants.

The domain and symbol terminology goes back to at least Ruby 2.3 (https://ruby-doc.org/stdlib-2.3.5/libdoc/socket/rdoc/Socket.html#method-c-new)