wifi_sniffer.rb

#
# Wi-Fi SSID Sniffer in 9 Lines of Ruby using Raw Sockets
#
# No Gem, no lib, just plain Ruby.
# You have to run it with root/sudo.
# My Ruby version is 1.9.3 and I run Linux.

require 'socket'

sock = Socket.new(Socket::PF_PACKET, Socket::SOCK_RAW, 0x03_00)
while true
  packet = sock.recvfrom(2048)[0].unpack('C*').pack('U*')
  next if packet.size < 60 || packet[40].ord != 80
  mac = packet[28..33].chars.map{|e|e.ord.to_s(16)}.join(':')
  name = packet[56..55+packet[55].ord]
  puts "#{Time.now}\t#{mac}\t#{name}"
end