valid-ipv4.rb

module Valid
  OCTET_RANGE = (0 .. 255)

  def self.ipv4?(address)
    octets = address.split '.'
    octets.length == 4 && octets.all? { |octet|
      octet_i = octet.to_i
      (0..255).cover?(octet_i) && octet_i.to_s(10) == octet
    }
  end
end

Valid.ipv4? "192.168.1.1"
# => true
Valid.ipv4? "192.168.1.1.1"
# => false
Valid.ipv4? "256.168.1.1"
# => false
Valid.ipv4? "256.168.1.0x1"
# => false
Valid.ipv4? "I would shiver the whole night through."
# => false