An example of Child/Parent communication.

master_child.rb

require 'yajl'

class MasterChild

  def initialize
    @child, @parent = IO.pipe
    start_master_process_thread
  end

  # This runs a thread that listens to child processes.
  #
  def start_master_process_thread
    # This thread is stopped in the children.
    #
    Thread.new do
      loop do
        IO.select([@child], nil, nil, 2) or next
        result = @child.gets ';;;'
        data = Yajl::Parser.parse result[0..-4]
        puts data
      end
    end
  end

  def send_to_parent data
    close_child
    write_parent data
  end
  # Write the parent.
  #
  # Note: The ; is the end marker for the message.
  #
  def write_parent data
    @parent.write "#{Yajl::Encoder.encode(data)};;;"
  end
  # Close the child if it isn't yet closed.
  #
  def close_child
    @child.close unless @child.closed?
  end

end

master_child = MasterChild.new

3.times do
  fork do
    loop do
      master_child.send_to_parent "Hello from child with pid #{Process.pid}."
      sleep rand*2
    end
  end
end

loop do
  sleep 1
end