em-rpc-server.rb

require 'rubygems'
require 'eventmachine'
require 'socket'

module RPCServer
  include EM::P::ObjectProtocol
  def post_init
    @obj = Hash.new
  end
  def receive_object method
    send_object @obj.__send__(*method)
  end
  def unbind
    @obj = nil
  end
end

unless defined?(BlankSlate)
  if defined?(BasicObject)
    BlankSlate = BasicObject
  else
    class BlankSlate
      instance_methods.each { |m| undef_method m unless m =~ /^__/ }
    end
  end
end

class RPCClient < BlankSlate
  def initialize sock = '/tmp/rpc.sock'
    @sock = UNIXSocket.open(sock)
  end
  def method_missing *meth
    data = Marshal.dump(meth)
    @sock.send([data.respond_to?(:bytesize) ? data.bytesize : data.size, data].pack('Na*'), 0)
    Marshal.load @sock.recv(*@sock.recv(4).unpack('N'))
  end
end

class AsyncRPCClient < BlankSlate
  module Handler
    include EM::P::ObjectProtocol
    def post_init
      @queue = []
    end
    attr_reader :queue
    def receive_object obj
      if cb = @queue.shift
        cb.call(obj)
      end
    end
  end
  def initialize sock = '/tmp/rpc.sock'
    @sock = EM.connect sock, Handler
  end
  def method_missing *meth, &blk
    @sock.queue << blk
    @sock.send_object(meth)
  end
end

EM.run{
  FileUtils.rm '/tmp/rpc.sock' if File.exists? '/tmp/rpc.sock'
  EM.start_server '/tmp/rpc.sock', RPCServer

  # use a thread because the client is blocking
  Thread.new{
    o = RPCClient.new
    o[1] = :a
    o[2] = :b
    o[3] = :c
    p o.keys
    p o.values
  }

  o = AsyncRPCClient.new
  o[:A] = 99
  o[:B] = 98
  o[:C] = 97
  o.keys{ |keys| p(keys) }
  o.values{ |vals| p(vals) }
}