LocalSocket and Data Loss

[ManuMies]

I'm using QLocalSocket (and QLocalServer) to create IPC in Windows and it works pretty nicely. But when there is lot of traffic, I'm starting to lose messages.

How I should implement IPC with local socket properly to prevent data loss?

[ManuMies]

Any ideas?

Some good example of local socket IPC would be very nice.

[ManuMies]

The problem still occurs.

How do you usually manage IPC in windows with Qt and so that it can endure some traffic? Alternatives to QLocalSocket? Or problem code example how to implement QLocalSocket for windows?

[yogeshgokul]

Kindly try to set QLocalServer::setMaxPendingConnections() higher up to 300.

[ManuMies]

What's the default value for maxpendingconnections in windows?

I doubt if this really is the problem, since isn't count of connections the number of local sockets connected to the local server? Because the problem exists even though I only have single use local socket sending and receiving lot of packages from the server.

This is how my code looks like:

QLocalSocket

Initialization:

iSocket = new QLocalSocket(this);
iSocket->connectToServer(aCallbackAddress);

iSocket = new QLocalSocket(this);
iSocket->connectToServer(aCallbackAddress);

To copy to clipboard, switch view to plain text mode 

Sending:

iSocket->flush();
int write = iSocket->write(aData.toAscii());
if (write == -1)
{
    success = false;
}
iSocket->waitForBytesWritten(MSG_TIMEOUT);
iSocket->flush();

iSocket->flush();
int write = iSocket->write(aData.toAscii());
if (write == -1)
{
    success = false;
}
iSocket->waitForBytesWritten(MSG_TIMEOUT);
iSocket->flush();

To copy to clipboard, switch view to plain text mode 

Receiving:

QString data = iSocket->readAll();

QString data = iSocket->readAll();

To copy to clipboard, switch view to plain text mode 

QLocalServer

Initialization:

iServer = new QLocalServer(this);
iSockets = new QMap<QLocalSocket*,QString>();
iServer->listen(aCallbackAddress);
connect(iServer, SIGNAL(newConnection()), SLOT(newConnectonHandle()));

iServer = new QLocalServer(this);
iSockets = new QMap<QLocalSocket*,QString>();
iServer->listen(aCallbackAddress);
connect(iServer, SIGNAL(newConnection()), SLOT(newConnectonHandle()));

To copy to clipboard, switch view to plain text mode 

Sending:

if (socket->write(aData.toAscii()) == WRITE_ERROR)
{
    success = false;
}
socket->waitForBytesWritten(MSG_TIMEOUT);
socket->flush();

if (socket->write(aData.toAscii()) == WRITE_ERROR)
{
    success = false;
}
socket->waitForBytesWritten(MSG_TIMEOUT);
socket->flush();

To copy to clipboard, switch view to plain text mode 

Receiving:

QLocalSocket* socket = 0;
for (int i=0; i < iSockets->keys().count(); i++)
{
    if (iSockets->keys().at(i)->bytesAvailable() >= (int)sizeof(quint16))// Socket has some data to read
    {
        socket = iSockets->keys().at(i);
        QString data = socket->readAll();
        QStringList messageArgs = data.split(MSG_DELIMETER);
        if (messageArgs.count()>2)
        {
        iSockets->insert(socket,messageArgs.at(2));
        }
        emit received(data);
    }
}

QLocalSocket* socket = 0;
for (int i=0; i < iSockets->keys().count(); i++)
{
    if (iSockets->keys().at(i)->bytesAvailable() >= (int)sizeof(quint16))// Socket has some data to read
    {
        socket = iSockets->keys().at(i);
        QString data = socket->readAll();
        QStringList messageArgs = data.split(MSG_DELIMETER);
        if (messageArgs.count()>2)
        {
        iSockets->insert(socket,messageArgs.at(2));
        }
        emit received(data);
    }
}

To copy to clipboard, switch view to plain text mode 

Do you see anything out of place here?

[ManuMies]

It feels a bit like having a monologue here, but I continue...

Got it working finally. I feel a bit silly to say, that I didn't take the Windows buffer in account. So to get it working, the message must have a some kind of delimiter at end, because when readyRead is called, the might be more than one message to be read.

One question though. How secure is QLocalSocket?

[ManuMies]

Up.

Question is still open.