QTcpSocket and QUdpSocket on Windows 10, blocked?

[SPlatten]

@KroMignon , the IT department has just unlocked the app in the firewall...hopefully now it will work.

[SPlatten]

@KroMignon , IT unlocked the firewall, I can see that the application that is broadcasting a packet using UDP is appearing on WireShark, but I am still not receiving the packet in the other application which has been unblocked in the firewall.

The connection source for this application:

pUDPsocket = new QUdpSocket(this);
pUDPsocket->bind(QHostAddress::LocalHost, 8124);
QObject::connect(pUDPsocket, &QUdpSocket::readyRead, this, &SckServer::udpRead);

My slot:

void SckServer::udpRead() {
    while( pUDPsocket->hasPendingDatagrams() ) {
        QNetworkDatagram datagram(pUDPsocket->receiveDatagram());
        ...
    }
}

It never gets into udpRead... The IP address resolves to 10.132.55.189 and the port is 8124.

[KroMignon]

@SPlatten said in QTcpSocket and QUdpSocket on Windows 10, blocked?:

pUDPsocket->bind(QHostAddress::LocalHost, 8124);

You should verify that bind did work:

if(!pUDPsocket->bind(QHostAddress::LocalHost, 8124))
{
   qWarn() << "Failed to bind UDP socket:" << pUDPsocket->errorString();
}

[SPlatten]

@KroMignon , thank you, interesting the bind is failing:

Failed to bind UDP socket: The address is protected.

[jsulm]

@SPlatten For ports bellow 10.000 you need privileges (like root on UNIX).

[SPlatten]

@jsulm , I was just looking at:
https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers#Well-known_ports

Whats preventing me choosing a port that is in use for something else? For example 13?

[KroMignon]

@SPlatten said in QTcpSocket and QUdpSocket on Windows 10, blocked?:

Whats preventing me choosing a port that is in use for something else? For example 13?

As already written by @jsulm , port numbers bellow 1000 are reserved for system. You need to have root rights to bind on them.
This is called security ;)

[jsulm]

@SPlatten said in QTcpSocket and QUdpSocket on Windows 10, blocked?:

Whats preventing me choosing a port that is in use for something else?

From the link you posted (and what I wrote before): "On Unix-like operating systems, a process must execute with superuser privileges to be able to bind a network socket to an IP address using one of the well-known ports."

[SPlatten]

@KroMignon , @jsulm , ok, I've changed the port to 30119 for UDP communications, which seems to work on one application, on the other application that is going to receive the broadcasts and act on them I'm getting:

Failed to bind UDP socket: The bound address is already in use

Both applications are running on the same laptop, how do I set-up the receiver so it can receive messages broadcast on the same IP and port 30119 ?

[KroMignon]

@SPlatten said in QTcpSocket and QUdpSocket on Windows 10, blocked?:

Both applications are running on the same laptop, how do I set-up the receiver so it can receive messages broadcast on the same IP and port 30119 ?

Do you want to bind each socket on same port?
So you have allow reusing same port:

if(!pUDPsocket->bind(QHostAddress::LocalHost, 8124, QAbstractSocket::ShareAddress | QAbstractSocket::ReuseAddressHint))
{
   qWarn() << "Failed to bind UDP socket:" << pUDPsocket->errorString();
}

[SPlatten]

@KroMignon , thank you, I literally just added exactly that, compiling now and will try.

[SPlatten]

@KroMignon , its working :)

[Kent-Dorfman]

@SPlatten said in QTcpSocket and QUdpSocket on Windows 10, blocked?:

The problem I'm having is the laptop is so locked down by the company IT that I'm not sure if it is causing problems, as I said, last week these same applications were communicating.

And therein is the problem...and it ticks me off to no end. If you cannot own and control your dev resources then you're just whizzin in the wind when you need to do real work. These dumb-acre kids who think they know and understand network security need to be taken to the wood shed and whipped with a willow switch when they start treating devs like office admin workers.

[SPlatten]

@Kent-Dorfman , this is a large corporate company dealing with the ministry of defence they take security and IT very seriously...it does make life very difficult, but they have deep pockets so the cost doesn't hurt them so much.

[DominicLeer]

You can check the Windows 10 firewall settings to make sure that your applications are allowed through. Just search for ""firewall"" in the Start menu and click on ""Windows Defender Firewall"". From there, you can click on ""Allow an app or feature through Windows Defender Firewall"" and make sure that your applications are checked.