QTcpSocket NetworkError with Wifi OK but Internet NOK

[Match0um]

@SGaist The issue occurs when the client tries to connect to the server :

• In the case where it works (ethernet cable plugged in the PC (client)) : If the client tries to connect to the server while the server is not listening, the client hits something like QAsbtractSocket::ConnectionRefusedError or QAbstractSocket::SocketTimeoutError.
• But in the case where it doesn't work (client doesn't have access to the internet), it hits QAbstractSocket::NetworkError without any delay.

I don't have any firewall parameter on my raspberry. Here is the AP config (hostapd.conf) :

country_code=FR
interface=wlan0
ssid=wifiAP
hw_mode=g
channel=7
wmm_enabled=0
macaddr_acl=0
ignore_broadcast_ssid=1
auth_algs=1
wpa=2
wpa_passphrase=passwrd
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

What I was thinking about, maybe the MAC address (or another parameter) of my PC or my raspberry is not authorized on the other device. I had connected the raspberry to the same ethernet network once few weeks ago. Maybe it changed something to the settings ?

[Match0um]

I can confim you guys that the issue comes from the client side.

With my client offline (so no ethernet cable plugged in), I can connect the PC to the raspberry in SSH with Putty or cmd.
So in Qt, I decided to change the port number to 22 (ssh) in _client->connectToHost(ip, port 22). The behavior is exactly the same as explained before. It fails when the client is offline, it works when the client is online.
So the issue comes from Qt, or my code. But I don't know what.

[Pablo J. Rogina]

@Match0um said in QTcpSocket NetworkError with Wifi OK but Internet NOK:

I hit NetworkError

Could you please share the error? Specially the error string...

[Match0um]

@Pablo-J-Rogina Hi, here is how I manage errors (I added the error string) :

connect(_client, SIGNAL(error(QAbstractSocket::SocketError)), this SLOT(error(QAbstractSocket::SocketError)));

void myClass::error(QAbstractSocket::SocketError error)
{
    qDebug() << "ERROR " << error;
    qDebug()<< "Error string "<<_client.errorString();
}

So in the App output I get :
"ERROR QAbstractSocket::NetworkError".
Error string "Host unreachable"

I also ran my code in debug mode but I have no additionnal information about the error :/

[Match0um]

Ok guys, I finally found what causes the problem :

It is in my method connectionWifi() :

void MyClass::connectionWifi()
{
    _connectionAttempts++;
    qDebug()<<"@@ Connection wifi";
    QString resultDisk;
    QProcess process;
    int returnCode = process.execute("netsh wlan connect name=wifiAp");

    process.start("netsh wlan show networks");
    process.waitForFinished();
    resultDisk = process.readAllStandardOutput();

    if(returnCode==0){
        if(resultDisk.contains("wifiAp")){
            ui->label_statutWifi->setText(tr("Détecté"));
            connection();
        }else{
            ui->label_statutWifi->setText(tr("Non connecté"));
            ui->label_connect->setText(tr("Outil non détecté"));
        }

    }else{
        ui->label_statutWifi->setText(tr("Wifi de la tablette éteind"));
        ui->label_connect->setText(tr("Activez le WiFi"));
    }
}

If I comment this line it works well :

int returnCode = process.execute("netsh wlan connect name=wifiAp");

I don't know why this line makes the code not working when the the ethernet cable is unplugged (the ethernet network has no link with the wifi network I am trying to connect to).

[JonB]

@Match0um said in QTcpSocket NetworkError with Wifi OK but Internet NOK:

int returnCode = process.execute("netsh wlan connect name=wifiAp");

Try unplugging ethernet cable and run netsh wlan connect name=wifiAp from a Command Prompt. What happens, does it block?

[Match0um]

@JonB It does not block when I run this command, I get the output " the connection request was successful"

[SGaist]

Then try again in your code but building the parameter list rather than passing the complete command as a string.

I guess there's an issue with the = part.

[Kent-Dorfman]

This post is deleted!

[Match0um]

@SGaist Did you mean something like that ? :

QString cmd = "netsh";
QStringList arguments;
arguments <<"wlan"<<"connect"<<"name=mScan";
int returnCode = process.execute(cmd, arguments);

It doesn't change the behavior, I have the output "the connection request was successful", it connects my PC to the wifi access point, but if I run this commend the connectToHost method hits NetworkError.

[JonB]

@Match0um
Yes, that is what @SGaist intended. We wanted to to verify that the element name=mScan was passed as a single argument.

Whatever the issue is, it must be related, somehow, to the consequences of (successfully) running the command, not the act of running the command itself.

[Pablo J. Rogina]

@Match0um said in QTcpSocket NetworkError with Wifi OK but Internet NOK:

Error string "Host unreachable"

This is a routing issue. You may want to capture and analyze network traffic (i.e. using Wireshark) to see what's going on under your Qt app depending on what connections (wireless or wired) you have on your client PC