Using QSocketNotifier to select on a char device.

Question

I wrote a char device driver and am now writing a QT \"wrapper\" which part of it is to get a signal to fire when the device becomes readable via the poll mechanism. I had

Answer 1

Your QSocketNotifer gets destroyed as soon as that if block ends. It doesn't stand a chance of reporting anything.

You must keep that socket notifier alive as long as you want that file to be monitored. The simplest way of doing that is probably keeping a QSocketNotifer* member in one of your classes.

Answer 2

I'll also mention that QSocketNotifier can be used to watch stdin using the following

#include "ConsoleReader.h"
#include <QTextStream>

#include <unistd.h> //Provides STDIN_FILENO

ConsoleReader::ConsoleReader(QObject *parent) :
    QObject(parent),
    notifier(STDIN_FILENO, QSocketNotifier::Read)
{
    connect(&notifier, SIGNAL(activated(int)), this, SLOT(text()));
}

void ConsoleReader::text()
{
    QTextStream qin(stdin);
    QString line = qin.readLine();
    emit textReceived(line);
}

---Header

#pragma once

#include <QObject>
#include <QSocketNotifier>

class ConsoleReader : public QObject
{
    Q_OBJECT
public:
    explicit ConsoleReader(QObject *parent = 0);
signals:
    void textReceived(QString message);
public slots:
    void text();
private:
    QSocketNotifier notifier;
};