Can I create QTcpServer in another thread?

Mr Pang

I want to create qtcpserver in a separate netns. So I create it like this.

QTcpServer *x11Server = nullptr;
std::thread thread1([&]{
        if(setns(open("/var/run/UE", O_RDONLY), CLONE_NEWNET)){
            perror("setns");
            exit(-1);
        }
        x11Server = new QTcpServer;
        x11Server->listen(QHostAddress::Any, 6010);
    });
connect(x11Server, &QTcpServer::newConnection, [=]{
//todo
});

I put it in another thread to avoid setns influencing current main thread.
In later code I will connect x11Server's sinal with something. Is this safe?

sierdzio

You definitely can create QTcpServer in another thread, it is safe and supported scenario. I am not sure if using std::thread for this purpose is good:

will it spin a new QEventLoop for that thread? I doubt it
connect() likely won't know that QueuedConnection has to be used - you need to remember to set it manually for all inter-thread connections (it's a good practice anyway)

J.Hilk

Going from the user in this thread
https://forum.qt.io/topic/59687/qthread-or-std-thread

I would say using Signal&Slots from an std::thread is near impossible 🤷‍♂️

sierdzio

Good to know, thanks.