broadcast ip interface on windows xp

[pawer]

Why Chat example doesn't work on Windows XP? In Linux or W2K seems to work.

The problem is the broadcast ip from interface:

foreach (QNetworkInterface interface, QNetworkInterface::allInterfaces()) {
        foreach (QNetworkAddressEntry entry, interface.addressEntries()) {
			  qDebug() << "IP: " << entry.ip().toString() <<
					  "\nNetmask " << entry.netmask().toString() <<
					  "\nBroadcast " << entry.broadcast().toString();
        }
}

foreach (QNetworkInterface interface, QNetworkInterface::allInterfaces()) {
        foreach (QNetworkAddressEntry entry, interface.addressEntries()) {
			  qDebug() << "IP: " << entry.ip().toString() <<
					  "\nNetmask " << entry.netmask().toString() <<
					  "\nBroadcast " << entry.broadcast().toString();
        }
}

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In Windows XP entry.broadcast() is Null in LAN ifaces also.

Thx. Selu.

[marcel]

Make sure you don't have any blocking software( antivirus, etc ) on WinXp.
Also, are you using by anychance IPv6? Because you don't have a broadcast addr there ( it's multicast ).

Regards

[pawer]

I've unistalled Nod32, but seems equal.

This is the output for WinXP:

Starting program: C:\chat/release\chat.exe
---Type <return> to continue, or q <return> to quit---
warning: iface: "{E48D2691-0A73-4F6F-BD24-3851400ED148}"

warning: IP: "192.168.0.3"
Mask: "255.255.255.0"
Broadcast: ""

warning: iface: "MS TCP Loopback interface"

warning: IP: "127.0.0.1"
Mask: ""
Broadcast: ""

[wysota]

Do you have the standard Windows firewall enabled?

[pawer]

It does the same. I think it's not a problem of firewalling, if I put QHostAddress::Broadcast it communicates well. In my Linux desktop the output is this:

"lo"
IP: "127.0.0.1"
Netmask "255.0.0.0"
Broadcast ""

IP: "0:0:0:0:0:0:0:1"
Netmask "FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF"
Broadcast ""

"eth0"
IP: "192.168.0.2"
Netmask "255.255.255.0"
Broadcast "192.168.0.255"

IP: "FE80:0:0:0:211:D8FF:FE0D:A1C3"
Netmask "FFFF:FFFF:FFFF:FFFF:0:0:0:0"
Broadcast ""

Thanks. Selu.

[wysota]

Did you run the application with administrative rights? Maybe your security level simply blocks access to broadcast?

[marcel]

I've unistalled Nod32, but seems equal.

This is the output for WinXP:

Hmm...
I'm not saying that Nod32 is bad software( hey, it's romanian ), but I have had problems before with it, after uninstalling it. Problems like connecting to the internet. I think it happened twice.

I didn't find a real solution either. I just reinstalled Windows( it wasn't my computer ).
I'm not saying you should reinstall also, but dig a little deeper.

Regards

[pawer]

In WinXP I run it with Administrator user in several machines and in Linux with an unpriviledged user. I'm going crazy

Thanks. Selu

[wysota]

Linux doesn't forbid you from using broadcast while WinXP could. How do other Qt network examples behave? Do they work correctly?

[marcel]

Open a "command prompt" ( console ) and type "ipconfig /all".
See if all the information is correct and complete.

Regards

[marcel]

How about computing the broadcast address yourself?
You have the IP addr and the subnet mask.
As far as I know, taking the binary representations of the two, the broadcast is:
bradcast = (~subnet) | ip;

Just saying...

Regards

[marcel]

This is how it's calculated by Qt, for Win2K

// calculate the broadcast address
            quint32 ip = entry.ip().toIPv4Address();
            quint32 mask = entry.netmask().toIPv4Address();
            quint32 broadcast = (ip & mask) | (0xFFFFFFFFU & ~mask);

// calculate the broadcast address
            quint32 ip = entry.ip().toIPv4Address();
            quint32 mask = entry.netmask().toIPv4Address();
            quint32 broadcast = (ip & mask) | (0xFFFFFFFFU & ~mask);

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However, the funny thing is, that for WinXP, there is no such calculation:

static QList<QNetworkInterfacePrivate *> interfaceListingWinXP()
{
    QList<QNetworkInterfacePrivate *> interfaces;
    IP_ADAPTER_ADDRESSES staticBuf[2]; // 2 is arbitrary
    PIP_ADAPTER_ADDRESSES pAdapter = staticBuf;
    ULONG bufSize = sizeof staticBuf;
 
    ULONG flags = GAA_FLAG_INCLUDE_ALL_INTERFACES |
                  GAA_FLAG_INCLUDE_PREFIX |
                  GAA_FLAG_SKIP_DNS_SERVER |
                  GAA_FLAG_SKIP_MULTICAST;
    ULONG retval = ptrGetAdaptersAddresses(AF_UNSPEC, flags, NULL, pAdapter, &bufSize);
    if (retval == ERROR_BUFFER_OVERFLOW) {
        // need more memory
        pAdapter = (IP_ADAPTER_ADDRESSES *)qMalloc(bufSize);
 
        // try again
        if (ptrGetAdaptersAddresses(AF_UNSPEC, flags, NULL, pAdapter, &bufSize) != ERROR_SUCCESS) {
            qFree(pAdapter);
            return interfaces;
        }
    } else if (retval != ERROR_SUCCESS) {
        // error
        return interfaces;
    }
 
    // iterate over the list and add the entries to our listing
    for (PIP_ADAPTER_ADDRESSES ptr = pAdapter; ptr; ptr = ptr->Next) {
        QNetworkInterfacePrivate *iface = new QNetworkInterfacePrivate;
        interfaces << iface;
 
        iface->index = 0;
        if (ptr->Length >= offsetof(IP_ADAPTER_ADDRESSES, Ipv6IfIndex))
            iface->index = ptr->Ipv6IfIndex;
        else if (ptr->IfIndex != 0)
            iface->index = ptr->IfIndex;
 
        iface->flags = QNetworkInterface::CanBroadcast;
        if (ptr->OperStatus == IfOperStatusUp)
            iface->flags |= QNetworkInterface::IsUp | QNetworkInterface::IsRunning;
        if ((ptr->Flags & IP_ADAPTER_NO_MULTICAST) == 0)
            iface->flags |= QNetworkInterface::CanMulticast;
 
        iface->name = QString::fromLocal8Bit(ptr->AdapterName);
        if (ptr->PhysicalAddressLength)
            iface->hardwareAddress = iface->makeHwAddress(ptr->PhysicalAddressLength,
                                                          ptr->PhysicalAddress);
        else
            // loopback if it has no address
            iface->flags |= QNetworkInterface::IsLoopBack;
 
        // The GetAdaptersAddresses call has an interesting semantic:
        // It can return a number N of addresses and a number M of prefixes.
        // But if you have IPv6 addresses, generally N > M.
        // I cannot find a way to relate the Address to the Prefix, aside from stopping
        // the iteration at the last Prefix entry and assume that it applies to all addresses
        // from that point on.
        PIP_ADAPTER_PREFIX pprefix = 0;
        if (ptr->Length >= offsetof(IP_ADAPTER_ADDRESSES, FirstPrefix))
            pprefix = ptr->FirstPrefix;
        for (PIP_ADAPTER_UNICAST_ADDRESS addr = ptr->FirstUnicastAddress; addr; addr = addr->Next) {
            QNetworkAddressEntry entry;
            entry.setIp(addressFromSockaddr(addr->Address.lpSockaddr));
            if (pprefix) {
                entry.setNetmask(netmaskFromPrefixLength(pprefix->PrefixLength, addr->Address.lpSockaddr->sa_family));
                pprefix = pprefix->Next ? pprefix->Next : pprefix;
            }
 
            iface->addressEntries << entry;
        }
    }
 
    if (pAdapter != staticBuf)
        qFree(pAdapter);
 
    return interfaces;
}

static QList<QNetworkInterfacePrivate *> interfaceListingWinXP()
{
    QList<QNetworkInterfacePrivate *> interfaces;
    IP_ADAPTER_ADDRESSES staticBuf[2]; // 2 is arbitrary
    PIP_ADAPTER_ADDRESSES pAdapter = staticBuf;
    ULONG bufSize = sizeof staticBuf;

    ULONG flags = GAA_FLAG_INCLUDE_ALL_INTERFACES |
                  GAA_FLAG_INCLUDE_PREFIX |
                  GAA_FLAG_SKIP_DNS_SERVER |
                  GAA_FLAG_SKIP_MULTICAST;
    ULONG retval = ptrGetAdaptersAddresses(AF_UNSPEC, flags, NULL, pAdapter, &bufSize);
    if (retval == ERROR_BUFFER_OVERFLOW) {
        // need more memory
        pAdapter = (IP_ADAPTER_ADDRESSES *)qMalloc(bufSize);

        // try again
        if (ptrGetAdaptersAddresses(AF_UNSPEC, flags, NULL, pAdapter, &bufSize) != ERROR_SUCCESS) {
            qFree(pAdapter);
            return interfaces;
        }
    } else if (retval != ERROR_SUCCESS) {
        // error
        return interfaces;
    }

    // iterate over the list and add the entries to our listing
    for (PIP_ADAPTER_ADDRESSES ptr = pAdapter; ptr; ptr = ptr->Next) {
        QNetworkInterfacePrivate *iface = new QNetworkInterfacePrivate;
        interfaces << iface;

        iface->index = 0;
        if (ptr->Length >= offsetof(IP_ADAPTER_ADDRESSES, Ipv6IfIndex))
            iface->index = ptr->Ipv6IfIndex;
        else if (ptr->IfIndex != 0)
            iface->index = ptr->IfIndex;

        iface->flags = QNetworkInterface::CanBroadcast;
        if (ptr->OperStatus == IfOperStatusUp)
            iface->flags |= QNetworkInterface::IsUp | QNetworkInterface::IsRunning;
        if ((ptr->Flags & IP_ADAPTER_NO_MULTICAST) == 0)
            iface->flags |= QNetworkInterface::CanMulticast;

        iface->name = QString::fromLocal8Bit(ptr->AdapterName);
        if (ptr->PhysicalAddressLength)
            iface->hardwareAddress = iface->makeHwAddress(ptr->PhysicalAddressLength,
                                                          ptr->PhysicalAddress);
        else
            // loopback if it has no address
            iface->flags |= QNetworkInterface::IsLoopBack;

        // The GetAdaptersAddresses call has an interesting semantic:
        // It can return a number N of addresses and a number M of prefixes.
        // But if you have IPv6 addresses, generally N > M.
        // I cannot find a way to relate the Address to the Prefix, aside from stopping
        // the iteration at the last Prefix entry and assume that it applies to all addresses
        // from that point on.
        PIP_ADAPTER_PREFIX pprefix = 0;
        if (ptr->Length >= offsetof(IP_ADAPTER_ADDRESSES, FirstPrefix))
            pprefix = ptr->FirstPrefix;
        for (PIP_ADAPTER_UNICAST_ADDRESS addr = ptr->FirstUnicastAddress; addr; addr = addr->Next) {
            QNetworkAddressEntry entry;
            entry.setIp(addressFromSockaddr(addr->Address.lpSockaddr));
            if (pprefix) {
                entry.setNetmask(netmaskFromPrefixLength(pprefix->PrefixLength, addr->Address.lpSockaddr->sa_family));
                pprefix = pprefix->Next ? pprefix->Next : pprefix;
            }

            iface->addressEntries << entry;
        }
    }

    if (pAdapter != staticBuf)
        qFree(pAdapter);

    return interfaces;
}

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These are taken from qnetworkinterface_win.cpp.
I'm using Qt 4.2.2.

I suggest doing as for Win2k to get the broadcast.

Regards

[pawer]

Thanks. I'm going to try it out.

[marcel]

I already told you:

quint32 ip = entry.ip().toIPv4Address();
            quint32 mask = entry.netmask().toIPv4Address();
            quint32 broadcast = (ip & mask) | (0xFFFFFFFFU & ~mask);
            entry.setBroadcast(QHostAddress((broadcast)));

quint32 ip = entry.ip().toIPv4Address();
            quint32 mask = entry.netmask().toIPv4Address();
            quint32 broadcast = (ip & mask) | (0xFFFFFFFFU & ~mask);
            entry.setBroadcast(QHostAddress((broadcast)));

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Actually the code is stolen from the Qt sources .

[pawer]

This works perfectly, in Qt 4.3.0rc1 this is solved.

Thanks.