Return array of local IP addresses

local_ip.rb

require 'socket'

# Base on answer from http://stackoverflow.com/questions/42566/getting-the-hostname-or-ip-in-ruby-on-rails

# return an array of local IP addresses
def local_ip
  orig, Socket.do_not_reverse_lookup = Socket.do_not_reverse_lookup, true  # turn off reverse DNS resolution temporarily

  UDPSocket.open do |s|
    s.connect '4.2.2.1', 1 # as this is UDP, no connection will actually be made
    s.addr.select {|ip| ip =~ /[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}/}.uniq
  end
ensure
  Socket.do_not_reverse_lookup = orig
end