#! /usr/bin/env elixir

defmodule NRFTP do
  def check(ipa) do
    {a, b, c, d} = ipa
    ip = "#{a}.#{b}.#{c}.#{d}"

    try do
      case :ftp.open(ipa, timeout: 700, dtimeout: 5000) do
        {:ok, c} ->
          case :ftp.user(c, ~c"guest", ~c"password") do
            :ok ->
              IO.puts(ip)
              :ftp.close(c)

            _ ->
              nil
          end

        _ ->
          nil
      end
    rescue
      _ -> nil
    catch
      _ -> nil
    end
  end
end

defmodule IPGen do
  def gen_ip do
    intip = Enum.random(0x1000000..0xE0000000)

    if (0xA000000 <= intip and intip <= 0xAFFFFFF) or
         (0x64400000 <= intip and intip <= 0x647FFFFF) or
         (0x7F000000 <= intip and intip <= 0x7FFFFFFF) or
         (0xA9FE0000 <= intip and intip <= 0xA9FEFFFF) or
         (0xAC100000 <= intip and intip <= 0xAC1FFFFF) or
         (0xC0000000 <= intip and intip <= 0xC0000007) or
         (0xC00000AA <= intip and intip <= 0xC00000AB) or
         (0xC0000200 <= intip and intip <= 0xC00002FF) or
         (0xC0A80000 <= intip and intip <= 0xC0A8FFFF) or
         (0xC6120000 <= intip and intip <= 0xC613FFFF) or
         (0xC6336400 <= intip and intip <= 0xC63364FF) or
         (0xCB007100 <= intip and intip <= 0xCB0071FF) or
         (0xF0000000 <= intip and intip <= 0xFFFFFFFF) do
      gen_ip()
    else
      <<a, b, c, d>> = <<intip::unsigned-integer-size(32)>>
      {a, b, c, d}
    end
  end

  def infinite do
    Stream.repeatedly(&gen_ip/0)
  end
end

IPGen.infinite()
|> Task.async_stream(&NRFTP.check/1, max_concurrency: 1024, ordered: false, timeout: :infinity)
|> Stream.run()