anchor.diff:    // Connect with IPv4 source addesses.
     for (var sourceAddress in ipV4SourceAddresses) {
       if (!v6Only) {
  -      asyncStart();  // Matching asyncEnd in server.listen above.
         var s = await connectFunction(InternetAddress.LOOPBACK_IP_V4,
                                      server.port,
                                      sourceAddress: sourceAddress);
  
positive.code:                    bool v6Only,
                     Function connectFunction,
                     Function closeDestroyFunction) async {
    asyncStart();
    var server = await ServerSocket.bind(bindAddress, 0, v6Only: v6Only);
    server.listen((s) {
      s.destroy();
      asyncEnd();
    }, onDone: () => asyncEnd());
  
    asyncStart();
  
negative.code:     }
    }
  
    await allConnected.future;
    await server.close();
    asyncEnd();
  }
  
  