ruby listener for Spark Core multicast presence announcement

spark_core_id_listener

require 'socket'
require 'ipaddr'

MULTICAST_ADDR = '224.0.1.187'
PORT = 5683

ip = IPAddr.new(MULTICAST_ADDR).hton + IPAddr.new('0.0.0.0').hton

sock = UDPSocket.new
sock.setsockopt(Socket::IPPROTO_IP, Socket::IP_ADD_MEMBERSHIP, ip)
sock.bind(Socket::INADDR_ANY, PORT)

loop do
  msg, info = sock.recvfrom(1024)
  id = msg[7, 12].bytes.map { |b| b.to_i.to_s(16) }.join
  puts "Spark Core IP: #{info[2]}"
  puts "           ID: #{id}"
end