anchor.diff:          end,
       ?P("ensure all receivers terminated"),
       [begin unlink(Rec), exit(Rec, kill) end || Rec <- Receivers],
  +    ?P("close listen socket"),
  +    (catch gen_tcp:close(LSock)),
       ?P("done"),
       Result.
   
       
   exchange(Config, LSock, Port, Payload, Control) ->
       %% spin up client
  -    _ClntRcv = spawn(
  +    _ClntRcv = spawn_link(
           fun () ->
                   ?P("connect"),
                   {ok, Client} =
  
positive.code: 			   {active, false},
  			   {reuseaddr, true}]),
      %% get all sockets to know failing ends
      {ok, Port} = inet:port(LSock),
      ?P("listen socket port number ~w", [Port]),
      Control = self(),
  
negative.code:     Workers = erlang:system_info(schedulers_online) * 2,
      ?P("Use ~w workers", [Workers]),
      Payload = crypto:strong_rand_bytes(32),
      {ok, LSock} = ?LISTEN(Config,
  			  0,
  			  [binary,
  