def pcap_sniff(interface)
  capture = Pcap::Capture.open_live( interface, 1500 )
  capture.setfilter('tcp')
  capture.each_packet do |pkt|
    data = pkt.tcp_data
    #File.open('test.txt', 'a') {|f| f.write "#{data}"}
    puts data.grep(/%PDF/) if data =~ /%PDF/
    puts data.grep(/%EOF/) if data =~ /%%EOF/
  end
end