echo_listener.rb

def echo_listener(socket, linklocal_addr, multicast_addr, multicast_port,
                  flags, msg_length)
  loop do
    # Listen for messages of up to specified length
    message, client = socket.recvfrom(msg_length)

    # Extract client information given as array and log connection
    addr_info = Addrinfo.new(client)

    # We are not interested in messages from our selves
    next if addr_info.ip_address == linklocal_addr

    # Write out the received message
    puts message

    # Only reply if a request is send. We will make infinite packet loops
    # in our network if we don't do this
    if(message.split.first == "[REQUEST]")
      puts "========= Sending echo REPLY to #{addr_info.ip_address}"
      socket.send("[REPLY]   Hello from #{addr_info.ip_address}",
                  flags, multicast_addr, multicast_port)
    end
  end
end