code: static byte[] validIpV4ToBytes(String ip) {
          int i;
          return new byte[] {
                  ipv4WordToByte(ip, 0, i = ip.indexOf('.', 1)),
                  ipv4WordToByte(ip, i + 1, i = ip.indexOf('.', i + 2)),
                  ipv4WordToByte(ip, i + 1, i = ip.indexOf('.', i + 2)),
                  ipv4WordToByte(ip, i + 1, ip.length())
          };
      }
docs: visible for tests