Is there a way to check availability local server with timeout in Qt?

[TomNow99]

Hello,

I have on my VirtualBox linux with samba server. I have connection only between server and pc with virtualBox ( server can't connect with internet ). Is there a way to check availability server and after 5 seconds say: "no"?

Something like:

checkAvailabilityServer("\\192.168.43.21", 5);

?

If no Qt, maybe Winapi c++?

[hskoglund]

curl to the rescue:

curl -m 5 smb://192.168.43.21/ShareName/CanaryFile.txt

If the SMB server is alive, curl l will return curl: (67) Login denied
If the SMB server is down, curl will return curl: (28) Connection timed out after 5000 milliseconds

[TomNow99]

@hskoglund Thank you. But I don't give one more important information: my host OS is Windows 10. Curl is linux command right?

[Cobra91151]

Hello!

You can try to use QTcpSocket class. Check out the connectToHost method: (https://doc.qt.io/qt-5/qabstractsocket.html#connectToHost) . Also, feel free to check the waitForConnected method as well: https://doc.qt.io/qt-5/qabstractsocket.html#waitForConnected

Example:

bool checkServerConnection() {
    QTcpSocket connectionSocket;
    connectionSocket.connectToHost("192.168.43.21", 5);
    connectionSocket.waitForConnected(5000); // 5 seconnds

    if (connectionSocket.state() == QTcpSocket::UnconnectedState) {
        connectionSocket.close();
        return false;
    }

    connectionSocket.close();
    return true;
}

Happy coding!

[TomNow99]

@Cobra91151 Thank you for answer. Tommorow I check it! :)

[Cobra91151]

@TomNow99 said in Is there a way to check availability local server with timeout in Qt?:

@hskoglund Thank you. But I don't give one more important information: my host OS is Windows 10. Curl is linux command right?

It is available for Windows OS as well. You can check out this link for more details: https://curl.haxx.se/download.html

[TomNow99]

@Cobra91151 @mrjj That QTcpSocket is very good. But what if I have situation that I don't want wait?

So I want only do:

QTcpSocket connectionSocket;
connectionSocket.connectToHost("192.168.43.21", port);
qDebug()<<connectionSocket.state();

I can no wait and always get "connected" when server is up and "notConnected" when server is down? This is only server on my virtualBox.

[jsulm]

@TomNow99 Then use https://doc.qt.io/qt-5/qabstractsocket.html#connected

[TomNow99]

@jsulm Thank you. But I have other problem: I want check when server is down and I can't connect. Something like:

QTcpSocket connectionSocket;
connect(connectionSocket, SIGNAL(cannotConnect()), this, SLOT(cannotConnectSlot()));
connectionSocket.connectToHost("192.168.43.21", port);

[jsulm]

@TomNow99 You could use a QTimer with a timeout and if you do not get connected() until timeout you can assume that you can't connect.

[TomNow99]

@jsulm I think about that, but I have many Qtimers :D

EDIT:

I want something like:

Run my server. And in my application I want check connect to this server every 3 seconds. If I can't connect I want write qDebug()<<"noConnection" and end checking.

[jsulm]

@TomNow99 I don't see any other solution as even a working connection needs some time to be established, you can't simply do the qDebug just after calling connectToHost()

[TomNow99]

@jsulm Hmmm. I tried add new Qthread and check connection in this Qthread, but I get error "Cannot create children for a parent that is in a different thread". My code:

myThreadClass::myThreadClass(QTcpSocket *connSocket): connectionSocket(connSocket)
{

}

myThreadClass::~myThreadClass()
{
    connectionSocket->close();
}

void myThreadClass::run()
{
    while(1)
    {
        connectionSocket->connectToHost("192.168.43.23", 139);
        connectionSocket->waitForConnected(3000);

        if(connectionSocket->state() == QTcpSocket::UnconnectedState)
        {
            connectionSocket->close();
            emit noConnection();
        }

        connectionSocket->close();
    }
}

In mainWindow i create myThread and started it. I add QTcpSocket pointer and get this error.

class myThreadClass: public QThread
{
    Q_OBJECT
public:
    myThreadClass(QTcpSocket *connSocket);
    ~myThreadClass();
    void run();

private:
    QTcpSocket *connectionSocket;

signals:
    void noConnection();
};

[jsulm]

This post is deleted!

[jsulm]

@TomNow99 said in Is there a way to check availability local server with timeout in Qt?:

while(1)

You're blocking event loop...
And the socket must be allocated in the thread where you want to use it.

[TomNow99]

@jsulm I would like to check still connection that I add while(1)

[jsulm]

@TomNow99 I'm still not sure why you want this complicated solution using a thread if you can have one using a timer...

[TomNow99]

@jsulm Hmmm, but how? Something like:

in QTimerSlot ( check evert 3 sec ) I have:

connectionSocket->connectToHost("192.168.43.23", 139);
timer2.start(1000); // maybe singleShot

and how to connect information from slotConnected and other QTimer?

slotConnected()
{
    result = true;
}

slotTimer2()
{
   if(result == false )
   {

   }
}

?

[jsulm]

@TomNow99 Yes, like this

[TomNow99]

@jsulm Thank you