@int main(int argc, char *argv[])
{
QLocalSocket * m_socket = new QLocalSocket();
m_socket->connectToServer("SomeServer"); //how to give server name or is it path...

if(m_socket->waitForConnected(1000))
{
//send a message to the server
QByteArray block;
QDataStream out(&block, QIODevice::WriteOnly);
out.setVersion(QDataStream::Qt_4_7);
out << "x";
out.device()->seek(0);
m_socket->write(block);
m_socket->flush();
QMessageBox box;
box.setText("mesage has been sent");
box.exec();
...
}

@

And this in Qt widget application

where to create the below function...

@
void MainWindow::messageReceived()
{

QLocalServer *m_pServer;
QLocalSocket *clientConnection = m_pServer->nextPendingConnection();

while (clientConnection->bytesAvailable() < (int)sizeof(quint32))
clientConnection->waitForReadyRead();

connect(clientConnection, SIGNAL(disconnected()),
clientConnection, SLOT(deleteLater()));

QDataStream in(clientConnection);
in.setVersion(QDataStream::Qt_4_7);
if (clientConnection->bytesAvailable() < (int)sizeof(quint16)) {
return;
}

QString message;
in >> message;

QMessageBox box;
box.setText(QString(message));
box.exec();
}@

I got both applications output but i didn't saw any communication between them.
Please help...

http://stackoverflow.com/questions/13061079/qlocalsocket-to-qlocalserver-message-being-corrupted-during-transfer

You need to use an IPC system like e.g. QLocalSocket/Server. Have a look at Qt's documentation for IPC examples