ipv4Part = ? [0 .. 255]{1,3} ? ;
ipv4     = ipv4Part , ".", ipv4Part , "." , ipv4Part , "." , ipv4Part , ;
ipv6     = ? Any https://tools.ietf.org/html/rfc4291 IPv6 address ? ;
name     = ? Any host name ? ;
address  = ipv4 | ipv6 | name ;

Examples:
  127.0.0.1
  [::1]
  [2600:1417:6000:198::255e]
  localhost
  www.example.com
