Hostlookup using QHostInfo

[doggrant]

Hi,

I have the following code to perform a host lookup

// Perform host lookup
m_DoLookup = true;
m_Lookupid = QHostInfo::lookupHost( Address, this, SLOT( SLOTGetHostIPAddress(QHostInfo)) );
 
// Start short lookup timeout
m_LookupTimer = new QTimer(this);
connect(m_LookupTimer, SIGNAL(timeout()), this, SLOT(SLOTLookupTimeout()));
m_LookupTimer->setSingleShot(true);
m_LookupTimer->start(1000);
 
// Wait for lookup timeout to complete
while( m_DoLookup )
{
qApp->processEvents();
}

// Perform host lookup
m_DoLookup = true;
m_Lookupid = QHostInfo::lookupHost( Address, this, SLOT( SLOTGetHostIPAddress(QHostInfo)) );

// Start short lookup timeout
m_LookupTimer = new QTimer(this);
connect(m_LookupTimer, SIGNAL(timeout()), this, SLOT(SLOTLookupTimeout()));
m_LookupTimer->setSingleShot(true);
m_LookupTimer->start(1000);

// Wait for lookup timeout to complete
while( m_DoLookup )
{
qApp->processEvents();
}

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The timeout slot is

void SLOTLookupTimeout()
{
	// abort host lookup
	QHostInfo::abortHostLookup( m_Lookupid );
}

void SLOTLookupTimeout()
{
	// abort host lookup
	QHostInfo::abortHostLookup( m_Lookupid );
}

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Now when the QHostInfo::abortHostLookup() is called, I am expecting it to then go into my SLOTGetHostIPAddress(), where I can check for the failure. However, it never goes in there, and always stays in my processEvents() while loop. Any thoughts why?

I have confirmed the id returned from QHostInfo::lookupHost() is the same as the one passed into QHostInfo::abortHostLookup(). Is it just the case that if i abort a lookup, i don't get anything back saying it has been aborted?

David

[doggrant]

I have also noticed that with the

QHostInfo::abortHostLookup( m_Lookupid );

and

m_Lookupid = QHostInfo::lookupHost( Address, this, SLOT( SLOTGetHostIPAddress(QHostInfo)) );

calls in my code, my application crashes on exit, whether the lookup completed or not. Not sure why this is yet, will try looking at this.

David

[doggrant]

Still non the wiser about what is causing the crash in my application. Calling the static blocking call,

QHostInfo fromName ( const QString & name )

To resolve the host name to ip address does not cause my application to crash, but any call to the static calls

lookupHost ( const QString & name, QObject * receiver, const char * member )

or

abortHostLookup ( int id )

Causes my application to have an access violtation in qt_call_post_routines(), which is called from the QApplication destructor. Anyone have any ideas why?

David

[mgoetz]

In which Qt version do you have the crash?

SLOTGetHostIPAddress won't be called if you abort.

[doggrant]

The crash is in QT 4.5.2.

I came to the conclusion this might be a QT issue, and am currently in the process of installing QT 4.6.1 on my system.

[doggrant]

Also, this is on Windows XP.

[mgoetz]

Great!
Please report back and tell if it fixes the issue.

[doggrant]

Good news. Upgrading to QT 4.6.1 has resolved the crash on exit of my applciation