QSocketNotifier: Socket notifiers cannot be enabled or disabled from another thread

SGaist

You'll have to redesign your pool a bit to ensure that your sockets are created in the context of the run method of your QThread subclass.

rktech

@SGaist I know, but how?

SGaist

You have to transfer the descriptor to your pool and there in your run method create new sockets when descriptors are added.

rktech

@SGaist Should I add this part of code to my Pool::add() method? (Of course with editing it)

QTcpSocket tcpSocket;

    if (!tcpSocket.setSocketDescriptor(socketDescriptor)) {
        emit error(tcpSocket.error());
        return;
    }

rktech

@SGaist I have (probably) successfully rewritten the Pool add method, but I have another problem. When I add this:

protected:
    void incomingConnection(qintptr socketDescriptor) override;

to myserver.h I get this error:

...\myserver.h:35: Chyba: only virtual member functions can be marked 'override'

(Chyba is Error in my local)
What I am doing wrong?

mrjj

Hi
well it is virtual https://doc.qt.io/qt-5/qtcpserver.html#incomingConnection
so does Pool inherit QTcpServer ?
The error you get says "Hey, i dont see that funtion in base class, so you cant use override"

rktech

@mrjj No, the server is build under the myserver class

rktech

This post is deleted!

rktech

@mrjj the header of server look like:

#ifndef MYSERVER_H
#define MYSERVER_H

#include <QObject>
#include <QDebug>
#include <QTcpServer>
#include <QTcpSocket>
#include <QString>
#include <QFile>
#include <QStandardPaths>
#include <QThread>
#include <QElapsedTimer>
#include <pool.h>
#include <QDateTime>
class MyServer : public QObject
{
    Q_OBJECT
public:
    explicit MyServer(QObject *parent = nullptr);

signals:

public slots:
    void newConnection();
    void onReadyRead();

private:
    QTcpServer *server;
    QList<QTcpSocket*>  _sockets;
    QString a;
    QString com;
    QTcpSocket *socket;
    QList<QTcpSocket*> sl;
/*protected:
    void incomingConnection(qintptr socketDescriptor) override;*/
};

#endif // MYSERVER_H

Christian Ehrlicher

Sorry but please learn C++ first. If you want to override a function from a class you should inherit from this class. So inherit from QTcpServer, override the function and do whatever you want to. This is basic c++ stuff...

rktech

@Christian-Ehrlicher That's the thing, that I didn't notice. Thanks

rktech

@Christian-Ehrlicher But I don't know, how to edit it.

rktech

I have rewritten half of my project to solve the problem:
myserver.h

#ifndef MYSERVER_H
#define MYSERVER_H
#include <QStringList>
#include <QTcpServer>
#include <QDateTime>
class MyServer : public QTcpServer
{
    Q_OBJECT

public:
    MyServer(QObject *parent = nullptr);

protected:
    void incomingConnection(qintptr socketDescriptor) override;

private:
    QStringList fortunes;
};

#endif // MYSERVER_H

myserver.cpp

#include "myserver.h"
#include "pool.h"
Pool p;

MyServer::MyServer(QObject *parent)
    : QTcpServer(parent)
{
    p.start();
}

void MyServer::incomingConnection(qintptr socketDescriptor)
{
QDateTime qdt;
p.add(socketDescriptor,qdt.time());
}

pool.h

#ifndef POOL_H
#define POOL_H
#include<QObject>
#include<QThread>
#include<QTcpSocket>
#include<QDateTime>
#include<QElapsedTimer>
class Pool : public QThread
{
    Q_OBJECT

protected:
    void run();
private:
    struct conn{
        QTcpSocket *s;
        QTime qdt;
    };
    QList<conn> x;
public:
    void add(int socketDescriptor, QTime qdt);
};
#endif // POOL_H

pool.cpp

#include "pool.h"
#include <QElapsedTimer>
void Pool::run()
{
QElapsedTimer qet;
qet.start();
while (true) {
    if(qet.elapsed()>=5000){
        foreach (conn y, x) {
            if(y.s==nullptr){
                qDebug()<<"empty";
                continue;
            }
            y.s->write("test");
            y.s->flush();
        }
        qet.restart();
    }
}
}
void Pool::add(int socketDescriptor, QTime qdt){
QTcpSocket* s = new QTcpSocket;
s->setSocketDescriptor(socketDescriptor);
s->write("1\n");
conn c;
c.s=s;
c.qdt=qdt;
x.append(c);
}

But I have still the same error:

QSocketNotifier: Socket notifiers cannot be enabled or disabled from another thread

What's wrong?

SGaist

Because your add method is called in the thread of the tcp server.

As I already told you, the socket creation must happen in the run function.

rktech

@SGaist I have solved it. I am creating a list of descriptors in add() method and then rewriting it like this:
pool.cpp

void Pool::run()
{
QElapsedTimer qet;
qet.start();
while (true) {
    if(!d.empty()){
        qDebug()<<"rewriting";
        for (int i = 0; i<d.size();i++) {
            desc des = d[i];
            conn con;
            QTcpSocket* soc = new QTcpSocket;
            soc->setSocketDescriptor(des.descriptor);
            con.s=soc;
            con.qdt=des.qt;
            d.removeAt(i);
            x.append(con);
        }
        qDebug()<<"done";
    }
    if(qet.elapsed()>=5000){
        foreach (conn y, x) {
            if(!y.s->isOpen()){
                qDebug()<<"empty";
                continue;
            }
            y.s->write("test");
            qDebug()<<"l";
            y.s->flush();
        }
        qet.restart();
    }
}
}
void Pool::add(int socketDescriptor, QTime qdt){
desc de;
de.descriptor=socketDescriptor;
de.qt=qdt;
d.append(de);
}

definitions of structs and lists in pool.h:

  struct conn{
        QTcpSocket *s;
        QTime qdt;
    };
    struct desc{
        qintptr descriptor;
        QTime qt;
    };
    QList<conn> x;
    QList<desc> d;

SGaist

You are missing one important thing: you are accessing a resource from two different threads. You should protect its access accordingly.

rktech

@SGaist In my last code it is fixed, right? If no, how to protect it correctly?

SGaist

When using a new technology it's always a good idea to start by reading the documentation.

rktech

@SGaist I have read it, but I didn't catch what should I edit in my code.

SGaist

Did you read the Synchronizing Threads chapter linked in it ?