Weird net/ftp behavior

probe.rb

STDOUT.sync = true

require "net/ftp"

root  = "tgftp.nws.noaa.gov"
total = 0
run   = true

puts ">> Probing max connections for: #{root}"

while run do
  begin
    print "."
    ftp = Net::FTP.new root
    ftp.passive
    ftp.debug_mode
    ftp.login
  rescue EOFError, Net::FTPTempError
    run = false
  else
    total += 1
  end
end

puts "\n>> Total connections: #{total}"