sm_client.rb

require 'sm_zmq'

client = SM::Control::Client.new

trap(:INT) { client.shutdown }

loop do
  puts client.status
  sleep 0.1
end

client.shutdown

sm_server.rb

require 'sm_zmq'

server = SM::Control::Server.new

trap(:INT) { server.shutdown }

loop do
  server.delegate
  sleep 0.1
end

server.shutdown

sm_zmq.rb

require 'zmq'

module SM
  module Control
    class Client
      def initialize(address="ipc://sm-control")
        @socket = ZMQ::Context.new.socket(ZMQ::REQ)
        @address = address
        connect
      end

      def connect
        @socket.connect(@address)
      end

      def msgpair(msg)
        while (arr = ZMQ.select(nil, [@socket], [@socket], 0.1)).nil?
        end 

        @socket.send(msg)

        while (arr = ZMQ.select([@socket], nil, [@socket], 0.1)).nil?
        end

        return @socket.recv
      end

      def status
        msgpair("STATUS")
      end

      def shutdown
        @socket.close
      end
    end

    class Server
      def initialize(address="ipc://sm-control")
        @socket = ZMQ::Context.new.socket(ZMQ::REP)
        @address = address
        bind
      end

      def bind
        @socket.bind(@address)
      end

      def next_message
        @socket.recv(ZMQ::NOBLOCK)
      rescue IOError
        bind
        retry
      end

      def delegate
        msg = next_message

        p msg

        case msg
        when "STATUS"
          @socket.send(SM::Status.new.status)
        end
      end

      def shutdown
        @socket.close
      end
    end
  end

  class Status
    def status
      rand.to_s
    end
  end
end