QTcpServer not reachable outside

MartinD

Hi,
I run QTcpServer and listen(QHostAddress::Any, 8081);. The server is reachable on localhost:8081. However, it is not reachable on 192.168.1.1:8081 (192.168.1.1 is local IP of the PC where the server runs). I completely turned off firewall. I use Windows 10. I also tried to run my server with admin privileges.

How to access my server on 192.168.1.1:8081?

raven-worx

@MartinD
instead of binding it to QHostAddress::Any, iterate over the available adresses and use the the address from the LAN interface you want the server to be available on:

QHostAddress address;
foreach(QHostAddress a, QNetworkInterface::allAddresses())
{
	// use the first non-localhost IPv4 address
	if( a != QHostAddress::LocalHost && a.toIPv4Address() )
	{
		address = a;
		break;
	}
}
...
Q_ASSERT( !address.isNull() );
server->listen( address, 8081 );

MartinD

The foreach loop returns these addresses on the PC:

QHostAddress("169.254.195.225")
QHostAddress("169.254.187.118")
QHostAddress("192.168.1.1")
QHostAddress("169.254.45.48")

I don't know what 169.254.x.x adresses are (as I use 192.168.1.x IP address range for my LAN). Anyway, listening on the first IP, which is 169.254.195.225, doesn't work.

I also tried to hardcode listen(QHostAddress("192.168.1.1")) and this also doesn't work - the server is not reachable on localhost::8081 and on 192.168.1.1:8081.

LuGRU

If You're using some sort of firewall make sure FW don't block Your app.
Using QHostAddress::Any will force server to listen on all available interfaces.

MartinD

As I already mentioned, the firewall is completely off (I use Windows 10 built-in firewall). I also have Avast - is there anything that could block ingoing traffic to my PC?

LuGRU

In old days (XP) when app was in FW and FW was disabled sometimes it did blocked app anyways, so better to double check if app is listed there.

Avast - dunno don't use.

Additionally check if listen() return true, i.e.:

    if (!_tcpServer->listen(QHostAddress::Any, port)) {
        qDebug() << "server error unable to listen:"
                 << _tcpServer->errorString();
    } else {
        qDebug() << "tcp server listen on:"
                 << _tcpServer->serverAddress()
                 << _tcpServer->serverPort()
                    ;
    }

Maybe another app uses port, i.e. Skype.

MartinD

It seems that the problem is connected with Microsoft Edge browser which blocks http request to my QTcpServer. When I run http://192.168.1.1:8081 in Edge I don't receive incoming connection in my QTcpServer. When I run http://192.168.1.1:8081 in any other browser, or http://localhost:8081 in Edge, it works.