I am using Qt and wish to write a class that will perform some network-type operations, similar to FTP/HTTP. The class needs to connect to lots of machines, one after the other but I need the applications UI to stay (relatively) responsive during this process, so the user can cancel the operation, exit the application, etc. My first thought was to use a separate thread for network stuff but the built-in Qt FTP/HTTP (and other) classes apparently avoid using threads and instead rely on signals and slots. So, I'd like to do something similar and was hoping I could do something like this:

class Foo : public QObject
{
  Q_OBJECT
public:
  void start();

signals:
  void next();

private slots:
  void nextJob();
};

void Foo::start()
{
  ...
  connect(this, SIGNAL(next()), this, SLOT(nextJob()));
  emit next();
}

void Foo::nextJob()
{
  // Process next 'chunk'

  if (workLeftToDo)
  {
    emit next();
  }
}


void Bar::StartOperation()
{
   Foo* foo = new Foo;
   foo->start();
}

However, this doesn't work and UI freezes until all operations have completed. I was hoping that emitting signals wouldn't actually call the slots immediately but would somehow be queued up by Qt, allowing the main UI to still operate.

So what do I need to do in order to make this work? How does Qt achieve this with the multitude of built-in classes that appear to perform lengthy tasks on a single thread?