Just a simple udp server that can be used as a registry.

registry.rb

require 'socket' 

# This is the main registry. 
# When an individual node is started, it first looks
# for the registry and provides its information so that
# other nodes can query this entity for the location of 
# said nodes. 
class Registry

  # Default initializement w/ setting the port
  # to 20000. 
  def initialize 
    @udp_listener_handle = UDPSocket.new 
    @default_port = 20000 
    @default_host = 'localhost'
    @registry = Hash.new 
  end 

  # Listen at standard port number 
  def listen 
    listen_backend(@default_port) 
  end 

private 
  
  #== Variables 

  # The udp handle for the service 
  attr_reader :udp_listener_handle 

  # The default port to listen to 
  attr_reader :default_port 

  # The default host to listen on 
  attr_reader :default_host 

  # The registry is stored as a hash. 
  # The keys are the port numbers, and the 
  # values are a short description. For the sake 
  # of this example, let's not worry about foreign hosts 
  attr_reader :registry

  #== Functions 

  # Register a node to the registry! 
  def register(portnum,description) 
    @registry[portnum] = description unless @registry.contains? portnum
  end 

  # TODO 
  def destroy(portnum) 
  end 

  # Listen to a specified port number. 
  def listen_backend(portnum) 
    @udp_listener_handle.bind(@default_host, @default_port) 
    
    puts "Registry started, listening at port #{@default_port}, host #{@default_host}"

   while true do 
     packet = @udp_listener_handle.recvfrom(1024) 
     puts "[#{packet[1]}]"
     puts "  #{packet[0]}"
   end 

  end 

end