# convert a dotted decimal IPv4 address to dotted binary format
  def ipv4_to_binary(ipv4addr)
    ia = ipv4addr.to_s.split('.')
    if ia.size != 4
      return "0.0.0.0"
    end
    output = ""
    i = 1
    for octett in ia
      output = output + octett.to_i.to_s(2).using("########","0",true)
      if i < 4
        output = output + "."
      end
      i += 1
    end
    return output
  end
  
  
  # convert a IPv4 adress in binary dotted format to a dotted IPv4 address
  def binary_to_ipv4(ipv4addr)
    ia = ipv4addr.to_s.split('.')
    if ia.size != 4
      return "0.0.0.0"
    end
    output = ""
    i = 1
    for octett in ia
      output = output + octett.to_s.to_i(2).to_s
      if i < 4
        output = output + "."
      end
      i += 1
    end
    return output
  end