find list of all accessible hostnames

Question

I have an application where a user can dynamically configure TCP connections between remote processes. I'd like to make sure the user input is valid, by providing them with a QComboBox that is pre-populated with all the valid hostnames on their network. Is there a way to find the list of hostnames using Qt?

If possible I'd like to do this on both windows and linux.

Answer 1

This can be achieved using Qt classes, but you'll also need to use system tools to gather the hostname information, and those tools are different between linux and windows. That said, with a simple preprocessor switch, we can use QProcess to call the right one, and pull the hostnames out of the result using a QRegExp:

// find valid hostnames
QStringList hostnames;
QRegExp hostnameRx("\\\\\\\\(.*)");
QProcess cmd(this);

#ifdef _WIN32
    cmd.start("cmd.exe");
    cmd.write("net view\r\n");
    cmd.write("exit\r\n");
#else
    cmd.start("smbtree", QStringList() << "--no-pass"); 
#endif // _WIN32

cmd.waitForFinished();  

while (!cmd.atEnd())
{
    QString line = cmd.readLine();
    hostnameRx.indexIn(line);
    if (!hostnameRx.cap(1).trimmed().isEmpty())
    {
        hostnames << hostnameRx.cap(1).trimmed();
    }
}

The regex strips the begining '\\' returned by both net view and smbtree, because QTcpSocket connections take hostnames without it.

Obviously, the QStringListcan be used to populate a QComboBox:

QComboBox* box = new QComboBox(this);
box->insertItems(0, hostnames);

NOTE: net view and smbtree are only going to show computers with accessible shares. You can try nmap for a more complete list of live hosts, but you're going to need to run as root and you'll still probably hit a lot of firewall issues.