# File lib_core/rucy/messenger.rb, line 57
    def pop
      @lock.synchronize{
        while (@sock_queue.empty? && @cmd_queue.empty?)
          @pop_cond.wait(@lock)
        end

        if (! @cmd_queue.empty?) then
          return @cmd_queue.shift
        elsif (! @sock_queue.empty?) then
          socket = @sock_queue.shift
          @push_cond.signal
          return socket
        end
      }
    end