Socket stops to accept connexion

A got a service listening for a while and today it stop to respond with this message:

```QIODevice::read (QTcpSocket): device not open```

I know this information may be not enough to diagnose the problem, but maybe someone has already seen this behavior. I've seen Chinese IPs connected, so they may have crafted buggy packets. Tufao 1.4.1 on Ubuntu 16.04.01 (Qt 5.5.1)