def once(opts)
      o = @state.merge opts
      o[:time] = Time.now.to_i
      o[:tags] = ((o[:tags] | ["once"]) rescue ["once"])
      @client << o
    end
def once(opts)
      o = @state.merge opts
      o[:time] = Time.now.to_i
      o[:tags] = ((o[:tags] | ["once"]) rescue ["once"])
      @client << o
    end
Issues an immediate update of the state with tag "once"
 set, but does not update the local state. Useful for transient errors.
 Opts are merged with the state.