Fix race condition allowing to run several instances of qBittorrent at the same time

AUTHORS

@@ -11,6 +11,10 @@ Contributors:
 * Christian Kandeler <zambesi@users.sourceforge.net>
 
 Code from other projects:
+* files src/qtsingleapp/*
+  copyright: Qt Software (Nokia)
+  license: LGPL
+
 * files src/ico.cpp src/ico.h
   copyright: Malte Starostik <malte@kde.org>
   license: LGPL

src/GUI.cpp

@@ -39,8 +39,6 @@
 #include <QDesktopServices>
 #include <QStatusBar>
 #include <QClipboard>
-#include <QLocalServer>
-#include <QLocalSocket>
 #include <QCloseEvent>
 #include <QShortcut>
 
@@ -69,11 +67,6 @@
 #include "qmacapplication.h"
 #endif
 
-#ifdef Q_WS_WIN
-#include <windows.h>
-const int UNLEN = 256;
-#endif
-
 using namespace libtorrent;
 
 #define TIME_TRAY_BALLOON 5000
@@ -133,7 +126,7 @@ GUI::GUI(QWidget *parent, QStringList torrentCmdLine) : QMainWindow(parent), dis
   connect(BTSession, SIGNAL(alternativeSpeedsModeChanged(bool)), this, SLOT(updateAltSpeedsBtn(bool)));
   connect(BTSession, SIGNAL(recursiveTorrentDownloadPossible(QTorrentHandle&)), this, SLOT(askRecursiveTorrentDownloadConfirmation(QTorrentHandle&)));
 #ifdef Q_WS_MAC
-  connect(static_cast<QMacApplication*>(qApp), SIGNAL(newFileOpenMacEvent(QStringList)), this, SLOT(processParams(QStringList)));
+  connect(static_cast<QMacApplication*>(qApp), SIGNAL(newFileOpenMacEvent(QString)), this, SLOT(processParams(QString)));
 #endif
 
   qDebug("create tabWidget");
@@ -177,28 +170,7 @@ GUI::GUI(QWidget *parent, QStringList torrentCmdLine) : QMainWindow(parent), dis
   BTSession->startUpTorrents();
   // Add torrent given on command line
   processParams(torrentCmdLine);
-  // Use a tcp server to allow only one instance of qBittorrent
-  localServer = new QLocalServer();
-  QString uid = "";
-#ifdef Q_WS_WIN
-  char buffer[UNLEN+1] = {0};
-  DWORD buffer_len = UNLEN + 1;
-  if (!GetUserNameA(buffer, &buffer_len))
-    uid = QString(buffer);
-#else
-  uid = QString::number(getuid());
-#endif
-#ifdef Q_WS_X11
-  if(QFile::exists(QDir::tempPath()+QDir::separator()+QString("qBittorrent-")+uid)) {
-    // Socket was not closed cleanly
-    std::cerr << "Warning: Local domain socket was not closed cleanly, deleting file...\n";
-    QFile::remove(QDir::tempPath()+QDir::separator()+QString("qBittorrent-")+uid);
-  }
-#endif
-  if (!localServer->listen("qBittorrent-"+uid)) {
-    std::cerr  << "Couldn't create socket, single instance mode won't work...\n";
-  }
-  connect(localServer, SIGNAL(newConnection()), this, SLOT(acceptConnection()));
+
   // Start connection checking timer
   guiUpdater = new QTimer(this);
   connect(guiUpdater, SIGNAL(timeout()), this, SLOT(updateGUI()));
@@ -285,8 +257,6 @@ GUI::~GUI() {
     delete systrayIcon;
     delete myTrayIconMenu;
   }
-  localServer->close();
-  delete localServer;
   delete tabs;
   // Keyboard shortcuts
   delete switchSearchShortcut;
@@ -447,24 +417,6 @@ void GUI::balloonClicked() {
   }
 }
 
-void GUI::acceptConnection() {
-  QLocalSocket *clientConnection = localServer->nextPendingConnection();
-  connect(clientConnection, SIGNAL(disconnected()), this, SLOT(readParamsOnSocket()));
-  qDebug("accepted connection from another instance");
-}
-
-void GUI::readParamsOnSocket() {
-  QLocalSocket *clientConnection = static_cast<QLocalSocket*>(sender());
-  if(clientConnection) {
-    const QByteArray &params = clientConnection->readAll();
-    if(!params.isEmpty()) {
-      processParams(QString::fromLocal8Bit(params.constData()).split("\n"));
-      qDebug("Received parameters from another instance");
-    }
-    clientConnection->deleteLater();
-  }
-}
-
 void GUI::askRecursiveTorrentDownloadConfirmation(QTorrentHandle &h) {
   if(QMessageBox::question(this, tr("Recursive download confirmation"), tr("The torrent %1 contains torrent files, do you want to proceed with their download?").arg(h.name()), QMessageBox::Yes|QMessageBox::No) == QMessageBox::Yes) {
     BTSession->recursiveTorrentDownload(h);
@@ -721,12 +673,15 @@ void GUI::on_actionOpen_triggered() {
 // This function parse the parameters and call
 // the right addTorrent function, considering
 // the parameter type.
+void GUI::processParams(const QString& params_str) {
+    processParams(params_str.split(" ", QString::SkipEmptyParts));
+}
+
 void GUI::processParams(const QStringList& params) {
   QSettings settings(QString::fromUtf8("qBittorrent"), QString::fromUtf8("qBittorrent"));
   const bool useTorrentAdditionDialog = settings.value(QString::fromUtf8("Preferences/Downloads/AdditionDialog"), true).toBool();
   foreach(QString param, params) {
     param = param.trimmed();
-    if(param.startsWith("--")) continue;
     if(param.startsWith(QString::fromUtf8("http://"), Qt::CaseInsensitive) || param.startsWith(QString::fromUtf8("ftp://"), Qt::CaseInsensitive) || param.startsWith(QString::fromUtf8("https://"), Qt::CaseInsensitive)) {
       BTSession->downloadFromUrl(param);
     }else{

src/GUI.h

@@ -43,7 +43,6 @@ class Bittorrent;
 class QTimer;
 class downloadFromURL;
 class SearchEngine;
-class QLocalServer;
 class QCloseEvent;
 class RSSImp;
 class QShortcut;
@@ -89,8 +88,6 @@ protected slots:
   void on_actionWebsite_triggered() const;
   void on_actionBugReport_triggered() const;
   void on_actionShow_console_triggered();
-  void readParamsOnSocket();
-  void acceptConnection();
   void balloonClicked();
   void writeSettings();
   void readSettings();
@@ -112,6 +109,7 @@ protected slots:
   void on_actionOpen_triggered();
   void updateGUI();
   void loadPreferences(bool configure_session=true);
+  void processParams(const QString& params);
   void processParams(const QStringList& params);
   void addTorrent(QString path);
   void addUnauthenticatedTracker(const QPair<QTorrentHandle,QString> &tracker);
@@ -165,8 +163,6 @@ private:
   SearchEngine *searchEngine;
   // RSS
   QPointer<RSSImp> rssWidget;
-  // Misc
-  QLocalServer *localServer;
 };
 
 #endif

src/headlessloader.h

@@ -33,12 +33,10 @@
 
 #include <QObject>
 #include <QCoreApplication>
-#include <QLocalServer>
-#include <QLocalSocket>
 #include "preferences.h"
 #include "bittorrent.h"
 
-class HeadlessLoader: QObject {
+class HeadlessLoader: public QObject {
   Q_OBJECT
 
 public:
@@ -52,20 +50,6 @@ public:
     BTSession->startUpTorrents();
     // Process command line parameters
     processParams(torrentCmdLine);
-    // Use a tcp server to allow only one instance of qBittorrent
-    localServer = new QLocalServer();
-    const QString &uid = QString::number(getuid());
-#ifdef Q_WS_X11
-    if(QFile::exists(QDir::tempPath()+QDir::separator()+QString("qBittorrent-")+uid)) {
-      // Socket was not closed cleanly
-      std::cerr << "Warning: Local domain socket was not closed cleanly, deleting file..." << std::endl;
-      QFile::remove(QDir::tempPath()+QDir::separator()+QString("qBittorrent-")+uid);
-    }
-#endif
-    if (!localServer->listen("qBittorrent-"+uid)) {
-      std::cerr  << "Couldn't create socket, single instance mode won't work..." << std::endl;
-    }
-    connect(localServer, SIGNAL(newConnection()), this, SLOT(acceptConnection()));
     // Display some information to the user
     std::cout << std::endl << "******** " << qPrintable(tr("Information")) << " ********" << std::endl;
     std::cout << qPrintable(tr("To control qBittorrent, access the Web UI at http://localhost:%1").arg(QString::number(Preferences::getWebUiPort()))) << std::endl;
@@ -77,7 +61,6 @@ public:
   }
 
   ~HeadlessLoader() {
-    delete localServer;
     delete BTSession;
   }
 
@@ -92,6 +75,10 @@ public slots:
     std::cout << qPrintable(msg) << std::endl;
   }
 
+  void processParams(const QString& params_str) {
+    processParams(params_str.split(" ", QString::SkipEmptyParts));
+  }
+
   // As program parameters, we can get paths or urls.
   // This function parse the parameters and call
   // the right addTorrent function, considering
@@ -99,7 +86,6 @@ public slots:
   void processParams(const QStringList& params) {
     foreach(QString param, params) {
       param = param.trimmed();
-      if(param.startsWith("--")) continue;
       if(param.startsWith(QString::fromUtf8("http://"), Qt::CaseInsensitive) || param.startsWith(QString::fromUtf8("ftp://"), Qt::CaseInsensitive) || param.startsWith(QString::fromUtf8("https://"), Qt::CaseInsensitive)) {
         BTSession->downloadFromUrl(param);
       }else{
@@ -112,26 +98,7 @@ public slots:
     }
   }
 
-  void acceptConnection() {
-    QLocalSocket *clientConnection = localServer->nextPendingConnection();
-    connect(clientConnection, SIGNAL(disconnected()), this, SLOT(readParamsOnSocket()));
-    qDebug("accepted connection from another instance");
-  }
-
-  void readParamsOnSocket() {
-    QLocalSocket *clientConnection = static_cast<QLocalSocket*>(sender());
-    if(clientConnection) {
-      const QByteArray &params = clientConnection->readAll();
-      if(!params.isEmpty()) {
-        processParams(QString(params).split("\n"));
-        qDebug("Received parameters from another instance");
-      }
-      clientConnection->deleteLater();
-    }
-  }
-
 private:
-  QLocalServer *localServer;
   Bittorrent *BTSession;
 
 };

src/main.cpp

@@ -33,7 +33,6 @@
 #include <QFile>
 
 #ifndef DISABLE_GUI
-#include <QApplication>
 #include <QMessageBox>
 #include <QStyleFactory>
 #include <QStyle>
@@ -41,19 +40,19 @@
 #include <QPushButton>
 #ifdef Q_WS_MAC
 #include "qmacapplication.h"
+#else
+#include "qtsingleapplication.h"
 #endif
 #include "GUI.h"
 #include "ico.h"
 #else
-#include <QCoreApplication>
+#include "qtsinglecoreapplication.h"
 #include <iostream>
 #include <stdio.h>
 #include "headlessloader.h"
 #endif
 
 #include <QSettings>
-#include <QLocalSocket>
-#include <sys/types.h>
 
 #if defined(Q_WS_X11) || defined(Q_WS_MAC)
 #include <signal.h>
@@ -61,20 +60,15 @@
 #include "stacktrace.h"
 #endif
 
-#ifdef Q_WS_WIN
-#include <windows.h>
-const int UNLEN = 256;
-#endif
-
 #include <stdlib.h>
 #include "misc.h"
 #include "preferences.h"
 
 #ifdef DISABLE_GUI
-QCoreApplication *app;
+QtSingleCoreApplication *app;
 #else
 #ifndef Q_WS_MAC
-QApplication *app;
+QtSingleApplication *app;
 #else
 QMacApplication *app;
 #endif
@@ -177,60 +171,42 @@ void useStyle(QApplication *app, QString style){
 // Main
 int main(int argc, char *argv[]){
   // Create Application
+  QString uid = misc::getUserIDString();
 #ifdef DISABLE_GUI
-  app = new QCoreApplication(argc, argv);
+  app = new QtSingleCoreApplication("qBittorrent-"+uid, argc, argv);
 #else
 #ifndef Q_WS_MAC
-  app = new QApplication(argc, argv);
+  app = new QtSingleApplication("qBittorrent-"+uid, argc, argv);
 #else
-  app = new QMacApplication(argc, argv);
+  app = new QMacApplication("qBittorrent-"+uid, argc, argv);
 #endif
 #endif
 
+  // Check if qBittorrent is already running for this user
+  if(app->isRunning()) {
+    qDebug("qBittorrent is already running for this user.");
+    //Pass program parameters if any
+    QString message;
+    for (int a = 1; a < argc; ++a) {
+      QString p = QString::fromLocal8Bit(argv[a]);
+      if(p.startsWith("--")) continue;
+      message += argv[a];
+      if (a < argc-1)
+        message += " ";
+    }
+    if(!message.isEmpty()) {
+      qDebug("Passing program parameters to running instance...");
+      app->sendMessage(message);
+    }
+    return 0;
+  }
+
   QString locale;
   QSettings settings(QString::fromUtf8("qBittorrent"), QString::fromUtf8("qBittorrent"));
 #ifndef DISABLE_GUI
   bool no_splash = false;
 #endif
 
-  //Check if there is another instance running
-  QLocalSocket localSocket;
-  QString uid;
-#ifdef Q_WS_WIN
-  char buffer[UNLEN+1] = {0};
-  DWORD buffer_len = UNLEN + 1;
-  if (!GetUserNameA(buffer, &buffer_len))
-    uid = QString(buffer);
-#else
-  uid = QString::number(getuid());
-#endif
-  localSocket.connectToServer("qBittorrent-"+uid, QIODevice::WriteOnly);
-  if (localSocket.waitForConnected(1000)){
-    std::cout << "Another qBittorrent instance is already running...\n";
-    // Send parameters
-    if(argc > 1){
-      QStringList params;
-      for(int i=1;i<argc;++i){
-        params << QString::fromLocal8Bit(argv[i]);
-        std::cout << argv[i] << '\n';
-      }
-      QByteArray block = params.join("\n").toLocal8Bit();
-      std::cout << "writting: " << block.data() << '\n';
-      std::cout << "size: " << block.size() << '\n';
-      uint val = localSocket.write(block);
-      if(localSocket.waitForBytesWritten(5000)){
-        std::cout << "written(" <<val<<"): " << block.data() << '\n';
-      }else{
-        std::cerr << "Writing to the socket timed out\n";
-      }
-      localSocket.disconnectFromServer();
-      std::cout << "disconnected\n";
-    }
-    localSocket.close();
-    delete app;
-    return 0;
-  }
-
   // Load translation
   locale = settings.value(QString::fromUtf8("Preferences/General/Locale"), QString()).toString();
   QTranslator translator;
@@ -339,9 +315,14 @@ int main(int argc, char *argv[]){
       splash->finish(window);
       delete splash;
     }
+    QObject::connect(app, SIGNAL(messageReceived(const QString&)),
+                     window, SLOT(processParams(const QString&)));
+    app->setActivationWindow(window);
 #else
     // Load Headless class
     HeadlessLoader *loader = new HeadlessLoader(torrentCmdLine);
+    QObject::connect(app, SIGNAL(messageReceived(const QString&)),
+                     loader, SLOT(processParams(const QString&)));
 #endif
     int ret =  app->exec();
 

src/misc.cpp

@@ -45,6 +45,11 @@
 
 #ifdef Q_WS_WIN
 #include <shlobj.h>
+#include <windows.h>
+const int UNLEN = 256;
+#else
+#include <unistd.h>
+#include <sys/types.h>
 #endif
 
 #ifdef Q_WS_MAC
@@ -545,6 +550,19 @@ QString misc::userFriendlyDuration(qlonglong seconds) {
   return QString::fromUtf8("∞");
 }
 
+QString misc::getUserIDString() {
+  QString uid = "0";
+#ifdef Q_WS_WIN
+  char buffer[UNLEN+1] = {0};
+  DWORD buffer_len = UNLEN + 1;
+  if (!GetUserNameA(buffer, &buffer_len))
+    uid = QString(buffer);
+#else
+  uid = QString::number(getuid());
+#endif
+  return uid;
+}
+
 QStringList misc::toStringList(const QList<bool> &l) {
   QStringList ret;
   foreach(const bool &b, l) {

src/misc.h

@@ -122,6 +122,7 @@ public:
   // Take a number of seconds and return an user-friendly
   // time duration like "1d 2h 10m".
   static QString userFriendlyDuration(qlonglong seconds);
+  static QString getUserIDString();
 
   // Convert functions
   static QStringList toStringList(const QList<bool> &l);

src/qmacapplication.cpp

@@ -33,8 +33,8 @@
 #include <QFileOpenEvent>
 #include "qmacapplication.h"
 
-QMacApplication::QMacApplication(int &argc, char** argv) :
-    QApplication(argc, argv)
+QMacApplication::QMacApplication(QString appid, int &argc, char** argv) :
+    QtSingleApplication(appid, argc, argv)
 {
 }
 
@@ -43,9 +43,8 @@ bool QMacApplication::event(QEvent * event) {
   switch (event->type()) {
   case QEvent::FileOpen:
     {
-      QStringList paths;
-      paths << static_cast<QFileOpenEvent *>(event)->file();
-      emit newFileOpenMacEvent(paths);
+      QString path = static_cast<QFileOpenEvent *>(event)->file();
+      emit newFileOpenMacEvent(path);
       return true;
     }
   default:

src/qmacapplication.h

@@ -32,17 +32,17 @@
 
 #ifdef Q_WS_MAC
 
-#include <QApplication>
+#include "qtsingleapplication.h"
 #include <QStringList>
 
-class QMacApplication : public QApplication
+class QMacApplication : public QtSingleApplication
 {
   Q_OBJECT
 public:
-  explicit QMacApplication(int &argc, char** argv);
+  explicit QMacApplication(QString appid, int &argc, char** argv);
 
 signals:
-  void newFileOpenMacEvent(QStringList paths);
+  void newFileOpenMacEvent(const QString &path);
 
 protected:
   bool event(QEvent *);

src/qtsingleapp/QtLockedFile

@@ -0,0 +1 @@
+#include "qtlockedfile.h"

src/qtsingleapp/QtSingleApplication

@@ -0,0 +1 @@
+#include "qtsingleapplication.h"

src/qtsingleapp/qtlocalpeer.cpp

@@ -0,0 +1,203 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+
+#include "qtlocalpeer.h"
+#include <QtCore/QCoreApplication>
+#include <QtCore/QTime>
+
+#if defined(Q_OS_WIN)
+#include <QtCore/QLibrary>
+#include <QtCore/qt_windows.h>
+typedef BOOL(WINAPI*PProcessIdToSessionId)(DWORD,DWORD*);
+static PProcessIdToSessionId pProcessIdToSessionId = 0;
+#endif
+#if defined(Q_OS_UNIX)
+#include <time.h>
+#endif
+
+namespace QtLP_Private {
+#include "qtlockedfile.cpp"
+#if defined(Q_OS_WIN)
+#include "qtlockedfile_win.cpp"
+#else
+#include "qtlockedfile_unix.cpp"
+#endif
+}
+
+const char* QtLocalPeer::ack = "ack";
+
+QtLocalPeer::QtLocalPeer(QObject* parent, const QString &appId)
+    : QObject(parent), id(appId)
+{
+    QString prefix = id;
+    if (id.isEmpty()) {
+        id = QCoreApplication::applicationFilePath();
+#if defined(Q_OS_WIN)
+        id = id.toLower();
+#endif
+        prefix = id.section(QLatin1Char('/'), -1);
+    }
+    prefix.remove(QRegExp("[^a-zA-Z]"));
+    prefix.truncate(6);
+
+    QByteArray idc = id.toUtf8();
+    quint16 idNum = qChecksum(idc.constData(), idc.size());
+    socketName = QLatin1String("qtsingleapp-") + prefix
+                 + QLatin1Char('-') + QString::number(idNum, 16);
+
+#if defined(Q_OS_WIN)
+    if (!pProcessIdToSessionId) {
+        QLibrary lib("kernel32");
+        pProcessIdToSessionId = (PProcessIdToSessionId)lib.resolve("ProcessIdToSessionId");
+    }
+    if (pProcessIdToSessionId) {
+        DWORD sessionId = 0;
+        pProcessIdToSessionId(GetCurrentProcessId(), &sessionId);
+        socketName += QLatin1Char('-') + QString::number(sessionId, 16);
+    }
+#else
+    socketName += QLatin1Char('-') + QString::number(::getuid(), 16);
+#endif
+
+    server = new QLocalServer(this);
+    QString lockName = QDir(QDir::tempPath()).absolutePath()
+                       + QLatin1Char('/') + socketName
+                       + QLatin1String("-lockfile");
+    lockFile.setFileName(lockName);
+    lockFile.open(QIODevice::ReadWrite);
+}
+
+
+
+bool QtLocalPeer::isClient()
+{
+    if (lockFile.isLocked())
+        return false;
+
+    if (!lockFile.lock(QtLP_Private::QtLockedFile::WriteLock, false))
+        return true;
+
+    bool res = server->listen(socketName);
+#if defined(Q_OS_UNIX) && (QT_VERSION >= QT_VERSION_CHECK(4,5,0))
+    // ### Workaround
+    if (!res && server->serverError() == QAbstractSocket::AddressInUseError) {
+        QFile::remove(QDir::cleanPath(QDir::tempPath())+QLatin1Char('/')+socketName);
+        res = server->listen(socketName);
+    }
+#endif
+    if (!res)
+        qWarning("QtSingleCoreApplication: listen on local socket failed, %s", qPrintable(server->errorString()));
+    QObject::connect(server, SIGNAL(newConnection()), SLOT(receiveConnection()));
+    return false;
+}
+
+
+bool QtLocalPeer::sendMessage(const QString &message, int timeout)
+{
+    if (!isClient())
+        return false;
+
+    QLocalSocket socket;
+    bool connOk = false;
+    for(int i = 0; i < 2; i++) {
+        // Try twice, in case the other instance is just starting up
+        socket.connectToServer(socketName);
+        connOk = socket.waitForConnected(timeout/2);
+        if (connOk || i)
+            break;
+        int ms = 250;
+#if defined(Q_OS_WIN)
+        Sleep(DWORD(ms));
+#else
+        struct timespec ts = { ms / 1000, (ms % 1000) * 1000 * 1000 };
+        nanosleep(&ts, NULL);
+#endif
+    }
+    if (!connOk)
+        return false;
+
+    QByteArray uMsg(message.toUtf8());
+    QDataStream ds(&socket);
+    ds.writeBytes(uMsg.constData(), uMsg.size());
+    bool res = socket.waitForBytesWritten(timeout);
+    res &= socket.waitForReadyRead(timeout);   // wait for ack
+    res &= (socket.read(qstrlen(ack)) == ack);
+    return res;
+}
+
+
+void QtLocalPeer::receiveConnection()
+{
+    QLocalSocket* socket = server->nextPendingConnection();
+    if (!socket)
+        return;
+
+    while (socket->bytesAvailable() < (int)sizeof(quint32))
+        socket->waitForReadyRead();
+    QDataStream ds(socket);
+    QByteArray uMsg;
+    quint32 remaining;
+    ds >> remaining;
+    uMsg.resize(remaining);
+    int got = 0;
+    char* uMsgBuf = uMsg.data();
+    do {
+        got = ds.readRawData(uMsgBuf, remaining);
+        remaining -= got;
+        uMsgBuf += got;
+    } while (remaining && got >= 0 && socket->waitForReadyRead(2000));
+    if (got < 0) {
+        qWarning() << "QtLocalPeer: Message reception failed" << socket->errorString();
+        delete socket;
+        return;
+    }
+    QString message(QString::fromUtf8(uMsg));
+    socket->write(ack, qstrlen(ack));
+    socket->waitForBytesWritten(1000);
+    delete socket;
+    emit messageReceived(message); //### (might take a long time to return)
+}

src/qtsingleapp/qtlocalpeer.h

@@ -0,0 +1,81 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+
+#include <QtNetwork/QLocalServer>
+#include <QtNetwork/QLocalSocket>
+#include <QtCore/QDir>
+
+namespace QtLP_Private {
+#include "qtlockedfile.h"
+}
+
+class QtLocalPeer : public QObject
+{
+    Q_OBJECT
+
+public:
+    QtLocalPeer(QObject *parent = 0, const QString &appId = QString());
+    bool isClient();
+    bool sendMessage(const QString &message, int timeout);
+    QString applicationId() const
+        { return id; }
+
+Q_SIGNALS:
+    void messageReceived(const QString &message);
+
+protected Q_SLOTS:
+    void receiveConnection();
+
+protected:
+    QString id;
+    QString socketName;
+    QLocalServer* server;
+    QtLP_Private::QtLockedFile lockFile;
+
+private:
+    static const char* ack;
+};

src/qtsingleapp/qtlockedfile.cpp

@@ -0,0 +1,199 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+#include "qtlockedfile.h"
+
+/*!
+    \class QtLockedFile
+
+    \brief The QtLockedFile class extends QFile with advisory locking
+    functions.
+
+    A file may be locked in read or write mode. Multiple instances of
+    \e QtLockedFile, created in multiple processes running on the same
+    machine, may have a file locked in read mode. Exactly one instance
+    may have it locked in write mode. A read and a write lock cannot
+    exist simultaneously on the same file.
+
+    The file locks are advisory. This means that nothing prevents
+    another process from manipulating a locked file using QFile or
+    file system functions offered by the OS. Serialization is only
+    guaranteed if all processes that access the file use
+    QLockedFile. Also, while holding a lock on a file, a process
+    must not open the same file again (through any API), or locks
+    can be unexpectedly lost.
+
+    The lock provided by an instance of \e QtLockedFile is released
+    whenever the program terminates. This is true even when the
+    program crashes and no destructors are called.
+*/
+
+/*! \enum QtLockedFile::LockMode
+
+    This enum describes the available lock modes.
+
+    \value ReadLock A read lock.
+    \value WriteLock A write lock.
+    \value NoLock Neither a read lock nor a write lock.
+*/
+
+/*!
+    Constructs an unlocked \e QtLockedFile object. This constructor
+    behaves in the same way as \e QFile::QFile().
+
+    \sa QFile::QFile()
+*/
+QtLockedFile::QtLockedFile()
+    : QFile()
+{
+#ifdef Q_OS_WIN
+    wmutex = 0;
+    rmutex = 0;
+#endif
+    m_lock_mode = NoLock;
+}
+
+/*!
+    Constructs an unlocked QtLockedFile object with file \a name. This
+    constructor behaves in the same way as \e QFile::QFile(const
+    QString&).
+
+    \sa QFile::QFile()
+*/
+QtLockedFile::QtLockedFile(const QString &name)
+    : QFile(name)
+{
+#ifdef Q_OS_WIN
+    wmutex = 0;
+    rmutex = 0;
+#endif
+    m_lock_mode = NoLock;
+}
+
+/*!
+  Opens the file in OpenMode \a mode.
+
+  This is identical to QFile::open(), with the one exception that the
+  Truncate mode flag is disallowed. Truncation would conflict with the
+  advisory file locking, since the file would be modified before the
+  write lock is obtained. If truncation is required, use resize(0)
+  after obtaining the write lock.
+
+  Returns true if successful; otherwise false.
+
+  \sa QFile::open(), QFile::resize()
+*/
+bool QtLockedFile::open(OpenMode mode)
+{
+    if (mode & QIODevice::Truncate) {
+        qWarning("QtLockedFile::open(): Truncate mode not allowed.");
+        return false;
+    }
+    return QFile::open(mode);
+}
+
+/*!
+    Returns \e true if this object has a in read or write lock;
+    otherwise returns \e false.
+
+    \sa lockMode()
+*/
+bool QtLockedFile::isLocked() const
+{
+    return m_lock_mode != NoLock;
+}
+
+/*!
+    Returns the type of lock currently held by this object, or \e
+    QtLockedFile::NoLock.
+
+    \sa isLocked()
+*/
+QtLockedFile::LockMode QtLockedFile::lockMode() const
+{
+    return m_lock_mode;
+}
+
+/*!
+    \fn bool QtLockedFile::lock(LockMode mode, bool block = true)
+
+    Obtains a lock of type \a mode. The file must be opened before it
+    can be locked.
+
+    If \a block is true, this function will block until the lock is
+    aquired. If \a block is false, this function returns \e false
+    immediately if the lock cannot be aquired.
+
+    If this object already has a lock of type \a mode, this function
+    returns \e true immediately. If this object has a lock of a
+    different type than \a mode, the lock is first released and then a
+    new lock is obtained.
+
+    This function returns \e true if, after it executes, the file is
+    locked by this object, and \e false otherwise.
+
+    \sa unlock(), isLocked(), lockMode()
+*/
+
+/*!
+    \fn bool QtLockedFile::unlock()
+
+    Releases a lock.
+
+    If the object has no lock, this function returns immediately.
+
+    This function returns \e true if, after it executes, the file is
+    not locked by this object, and \e false otherwise.
+
+    \sa lock(), isLocked(), lockMode()
+*/
+
+/*!
+    \fn QtLockedFile::~QtLockedFile()
+
+    Destroys the \e QtLockedFile object. If any locks were held, they
+    are released.
+*/

src/qtsingleapp/qtlockedfile.h

@@ -0,0 +1,101 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+#ifndef QTLOCKEDFILE_H
+#define QTLOCKEDFILE_H
+
+#include <QtCore/QFile>
+#ifdef Q_OS_WIN
+#include <QtCore/QVector>
+#endif
+
+#if defined(Q_WS_WIN)
+#  if !defined(QT_QTLOCKEDFILE_EXPORT) && !defined(QT_QTLOCKEDFILE_IMPORT)
+#    define QT_QTLOCKEDFILE_EXPORT
+#  elif defined(QT_QTLOCKEDFILE_IMPORT)
+#    if defined(QT_QTLOCKEDFILE_EXPORT)
+#      undef QT_QTLOCKEDFILE_EXPORT
+#    endif
+#    define QT_QTLOCKEDFILE_EXPORT __declspec(dllimport)
+#  elif defined(QT_QTLOCKEDFILE_EXPORT)
+#    undef QT_QTLOCKEDFILE_EXPORT
+#    define QT_QTLOCKEDFILE_EXPORT __declspec(dllexport)
+#  endif
+#else
+#  define QT_QTLOCKEDFILE_EXPORT
+#endif
+
+class QT_QTLOCKEDFILE_EXPORT QtLockedFile : public QFile
+{
+public:
+    enum LockMode { NoLock = 0, ReadLock, WriteLock };
+
+    QtLockedFile();
+    QtLockedFile(const QString &name);
+    ~QtLockedFile();
+
+    bool open(OpenMode mode);
+
+    bool lock(LockMode mode, bool block = true);
+    bool unlock();
+    bool isLocked() const;
+    LockMode lockMode() const;
+
+private:
+#ifdef Q_OS_WIN
+    Qt::HANDLE wmutex;
+    Qt::HANDLE rmutex;
+    QVector<Qt::HANDLE> rmutexes;
+    QString mutexname;
+
+    Qt::HANDLE getMutexHandle(int idx, bool doCreate);
+    bool waitMutex(Qt::HANDLE mutex, bool doBlock);
+
+#endif
+    LockMode m_lock_mode;
+};
+
+#endif

src/qtsingleapp/qtlockedfile_unix.cpp

@@ -0,0 +1,121 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "qtlockedfile.h"
+
+bool QtLockedFile::lock(LockMode mode, bool block)
+{
+    if (!isOpen()) {
+        qWarning("QtLockedFile::lock(): file is not opened");
+        return false;
+    }
+ 
+    if (mode == NoLock)
+        return unlock();
+           
+    if (mode == m_lock_mode)
+        return true;
+
+    if (m_lock_mode != NoLock)
+        unlock();
+
+    struct flock fl;
+    fl.l_whence = SEEK_SET;
+    fl.l_start = 0;
+    fl.l_len = 0;
+    fl.l_type = (mode == ReadLock) ? F_RDLCK : F_WRLCK;
+    int cmd = block ? F_SETLKW : F_SETLK;
+    int ret = fcntl(handle(), cmd, &fl);
+    
+    if (ret == -1) {
+        if (errno != EINTR && errno != EAGAIN)
+            qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
+        return false;
+    }
+
+    
+    m_lock_mode = mode;
+    return true;
+}
+
+
+bool QtLockedFile::unlock()
+{
+    if (!isOpen()) {
+        qWarning("QtLockedFile::unlock(): file is not opened");
+        return false;
+    }
+
+    if (!isLocked())
+        return true;
+
+    struct flock fl;
+    fl.l_whence = SEEK_SET;
+    fl.l_start = 0;
+    fl.l_len = 0;
+    fl.l_type = F_UNLCK;
+    int ret = fcntl(handle(), F_SETLKW, &fl);
+    
+    if (ret == -1) {
+        qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
+        return false;
+    }
+    
+    m_lock_mode = NoLock;
+    return true;
+}
+
+QtLockedFile::~QtLockedFile()
+{
+    if (isOpen())
+        unlock();
+}
+

src/qtsingleapp/qtlockedfile_win.cpp

@@ -0,0 +1,213 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+#include "qtlockedfile.h"
+#include <qt_windows.h>
+#include <QtCore/QFileInfo>
+
+#define MUTEX_PREFIX "QtLockedFile mutex "
+// Maximum number of concurrent read locks. Must not be greater than MAXIMUM_WAIT_OBJECTS
+#define MAX_READERS MAXIMUM_WAIT_OBJECTS
+
+Qt::HANDLE QtLockedFile::getMutexHandle(int idx, bool doCreate)
+{
+    if (mutexname.isEmpty()) {
+        QFileInfo fi(*this);
+        mutexname = QString::fromLatin1(MUTEX_PREFIX)
+                    + fi.absoluteFilePath().toLower();
+    }
+    QString mname(mutexname);
+    if (idx >= 0)
+        mname += QString::number(idx);
+
+    Qt::HANDLE mutex;
+    if (doCreate) {
+        QT_WA( { mutex = CreateMutexW(NULL, FALSE, (TCHAR*)mname.utf16()); },
+               { mutex = CreateMutexA(NULL, FALSE, mname.toLocal8Bit().constData()); } );
+        if (!mutex) {
+            qErrnoWarning("QtLockedFile::lock(): CreateMutex failed");
+            return 0;
+        }
+    }
+    else {
+        QT_WA( { mutex = OpenMutexW(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, (TCHAR*)mname.utf16()); },
+               { mutex = OpenMutexA(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, mname.toLocal8Bit().constData()); } );
+        if (!mutex) {
+            if (GetLastError() != ERROR_FILE_NOT_FOUND)
+                qErrnoWarning("QtLockedFile::lock(): OpenMutex failed");
+            return 0;
+        }
+    }
+    return mutex;
+}
+
+bool QtLockedFile::waitMutex(Qt::HANDLE mutex, bool doBlock)
+{
+    Q_ASSERT(mutex);
+    DWORD res = WaitForSingleObject(mutex, doBlock ? INFINITE : 0);
+    switch (res) {
+    case WAIT_OBJECT_0:
+    case WAIT_ABANDONED:
+        return true;
+        break;
+    case WAIT_TIMEOUT:
+        break;
+    default:
+        qErrnoWarning("QtLockedFile::lock(): WaitForSingleObject failed");
+    }
+    return false;
+}
+
+
+
+bool QtLockedFile::lock(LockMode mode, bool block)
+{
+    if (!isOpen()) {
+        qWarning("QtLockedFile::lock(): file is not opened");
+        return false;
+    }
+
+    if (mode == NoLock)
+        return unlock();
+
+    if (mode == m_lock_mode)
+        return true;
+
+    if (m_lock_mode != NoLock)
+        unlock();
+
+    if (!wmutex && !(wmutex = getMutexHandle(-1, true)))
+        return false;
+
+    if (!waitMutex(wmutex, block))
+        return false;
+
+    if (mode == ReadLock) {
+        int idx = 0;
+        for (; idx < MAX_READERS; idx++) {
+            rmutex = getMutexHandle(idx, false);
+            if (!rmutex || waitMutex(rmutex, false))
+                break;
+            CloseHandle(rmutex);
+        }
+        bool ok = true;
+        if (idx >= MAX_READERS) {
+            qWarning("QtLockedFile::lock(): too many readers");
+            rmutex = 0;
+            ok = false;
+        }
+        else if (!rmutex) {
+            rmutex = getMutexHandle(idx, true);
+            if (!rmutex || !waitMutex(rmutex, false))
+                ok = false;
+        }
+        if (!ok && rmutex) {
+            CloseHandle(rmutex);
+            rmutex = 0;
+        }
+        ReleaseMutex(wmutex);
+        if (!ok)
+            return false;
+    }
+    else {
+        Q_ASSERT(rmutexes.isEmpty());
+        for (int i = 0; i < MAX_READERS; i++) {
+            Qt::HANDLE mutex = getMutexHandle(i, false);
+            if (mutex)
+                rmutexes.append(mutex);
+        }
+        if (rmutexes.size()) {
+            DWORD res = WaitForMultipleObjects(rmutexes.size(), rmutexes.constData(),
+                                               TRUE, block ? INFINITE : 0);
+            if (res != WAIT_OBJECT_0 && res != WAIT_ABANDONED) {
+                if (res != WAIT_TIMEOUT)
+                    qErrnoWarning("QtLockedFile::lock(): WaitForMultipleObjects failed");
+                m_lock_mode = WriteLock;  // trick unlock() to clean up - semiyucky
+                unlock();
+                return false;
+            }
+        }
+    }
+
+    m_lock_mode = mode;
+    return true;
+}
+
+bool QtLockedFile::unlock()
+{
+    if (!isOpen()) {
+        qWarning("QtLockedFile::unlock(): file is not opened");
+        return false;
+    }
+
+    if (!isLocked())
+        return true;
+
+    if (m_lock_mode == ReadLock) {
+        ReleaseMutex(rmutex);
+        CloseHandle(rmutex);
+        rmutex = 0;
+    }
+    else {
+        foreach(Qt::HANDLE mutex, rmutexes) {
+            ReleaseMutex(mutex);
+            CloseHandle(mutex);
+        }
+        rmutexes.clear();
+        ReleaseMutex(wmutex);
+    }
+
+    m_lock_mode = QtLockedFile::NoLock;
+    return true;
+}
+
+QtLockedFile::~QtLockedFile()
+{
+    if (isOpen())
+        unlock();
+    if (wmutex)
+        CloseHandle(wmutex);
+}

src/qtsingleapp/qtsingleapplication.cpp

@@ -0,0 +1,351 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+
+#include "qtsingleapplication.h"
+#include "qtlocalpeer.h"
+#include <QtGui/QWidget>
+
+
+/*!
+    \class QtSingleApplication qtsingleapplication.h
+    \brief The QtSingleApplication class provides an API to detect and
+    communicate with running instances of an application.
+
+    This class allows you to create applications where only one
+    instance should be running at a time. I.e., if the user tries to
+    launch another instance, the already running instance will be
+    activated instead. Another usecase is a client-server system,
+    where the first started instance will assume the role of server,
+    and the later instances will act as clients of that server.
+
+    By default, the full path of the executable file is used to
+    determine whether two processes are instances of the same
+    application. You can also provide an explicit identifier string
+    that will be compared instead.
+
+    The application should create the QtSingleApplication object early
+    in the startup phase, and call isRunning() or sendMessage() to
+    find out if another instance of this application is already
+    running. Startup parameters (e.g. the name of the file the user
+    wanted this new instance to open) can be passed to the running
+    instance in the sendMessage() function.
+
+    If isRunning() or sendMessage() returns false, it means that no
+    other instance is running, and this instance has assumed the role
+    as the running instance. The application should continue with the
+    initialization of the application user interface before entering
+    the event loop with exec(), as normal. The messageReceived()
+    signal will be emitted when the application receives messages from
+    another instance of the same application.
+
+    If isRunning() or sendMessage() returns true, another instance is
+    already running, and the application should terminate or enter
+    client mode.
+
+    If a message is received it might be helpful to the user to raise
+    the application so that it becomes visible. To facilitate this,
+    QtSingleApplication provides the setActivationWindow() function
+    and the activateWindow() slot.
+
+    Here's an example that shows how to convert an existing
+    application to use QtSingleApplication. It is very simple and does
+    not make use of all QtSingleApplication's functionality (see the
+    examples for that).
+
+    \code
+    // Original
+    int main(int argc, char **argv)
+    {
+        QApplication app(argc, argv);
+
+        MyMainWidget mmw;
+
+        mmw.show();
+        return app.exec();
+    }
+
+    // Single instance
+    int main(int argc, char **argv)
+    {
+        QtSingleApplication app(argc, argv);
+
+        if (app.isRunning())
+            return 0;
+
+        MyMainWidget mmw;
+
+        app.setActivationWindow(&mmw);
+
+        mmw.show();
+        return app.exec();
+    }
+    \endcode
+
+    Once this QtSingleApplication instance is destroyed(for example,
+    when the user quits), when the user next attempts to run the
+    application this instance will not, of course, be encountered. The
+    next instance to call isRunning() or sendMessage() will assume the
+    role as the new running instance.
+
+    For console (non-GUI) applications, QtSingleCoreApplication may be
+    used instead of this class, to avoid the dependency on the QtGui
+    library.
+
+    \sa QtSingleCoreApplication
+*/
+
+
+void QtSingleApplication::sysInit(const QString &appId)
+{
+    actWin = 0;
+    peer = new QtLocalPeer(this, appId);
+    connect(peer, SIGNAL(messageReceived(const QString&)), SIGNAL(messageReceived(const QString&)));
+}
+
+
+/*!
+    Creates a QtSingleApplication object. The application identifier
+    will be QCoreApplication::applicationFilePath(). \a argc, \a
+    argv, and \a GUIenabled are passed on to the QAppliation constructor.
+
+    If you are creating a console application (i.e. setting \a
+    GUIenabled to false), you may consider using
+    QtSingleCoreApplication instead.
+*/
+
+QtSingleApplication::QtSingleApplication(int &argc, char **argv, bool GUIenabled)
+    : QApplication(argc, argv, GUIenabled)
+{
+    sysInit();
+}
+
+
+/*!
+    Creates a QtSingleApplication object with the application
+    identifier \a appId. \a argc and \a argv are passed on to the
+    QAppliation constructor.
+*/
+
+QtSingleApplication::QtSingleApplication(const QString &appId, int &argc, char **argv)
+    : QApplication(argc, argv)
+{
+    sysInit(appId);
+}
+
+
+/*!
+    Creates a QtSingleApplication object. The application identifier
+    will be QCoreApplication::applicationFilePath(). \a argc, \a
+    argv, and \a type are passed on to the QAppliation constructor.
+*/
+QtSingleApplication::QtSingleApplication(int &argc, char **argv, Type type)
+    : QApplication(argc, argv, type)
+{
+    sysInit();
+}
+
+
+#if defined(Q_WS_X11)
+/*!
+  Special constructor for X11, ref. the documentation of
+  QApplication's corresponding constructor. The application identifier
+  will be QCoreApplication::applicationFilePath(). \a dpy, \a visual,
+  and \a cmap are passed on to the QApplication constructor.
+*/
+QtSingleApplication::QtSingleApplication(Display* dpy, Qt::HANDLE visual, Qt::HANDLE cmap)
+    : QApplication(dpy, visual, cmap)
+{
+    sysInit();
+}
+
+/*!
+  Special constructor for X11, ref. the documentation of
+  QApplication's corresponding constructor. The application identifier
+  will be QCoreApplication::applicationFilePath(). \a dpy, \a argc, \a
+  argv, \a visual, and \a cmap are passed on to the QApplication
+  constructor.
+*/
+QtSingleApplication::QtSingleApplication(Display *dpy, int &argc, char **argv, Qt::HANDLE visual, Qt::HANDLE cmap)
+    : QApplication(dpy, argc, argv, visual, cmap)
+{
+    sysInit();
+}
+
+/*!
+  Special constructor for X11, ref. the documentation of
+  QApplication's corresponding constructor. The application identifier
+  will be \a appId. \a dpy, \a argc, \a
+  argv, \a visual, and \a cmap are passed on to the QApplication
+  constructor.
+*/
+QtSingleApplication::QtSingleApplication(Display* dpy, const QString &appId, int argc, char **argv, Qt::HANDLE visual, Qt::HANDLE cmap)
+    : QApplication(dpy, argc, argv, visual, cmap)
+{
+    sysInit(appId);
+}
+#endif
+
+
+/*!
+    Returns true if another instance of this application is running;
+    otherwise false.
+
+    This function does not find instances of this application that are
+    being run by a different user (on Windows: that are running in
+    another session).
+
+    \sa sendMessage()
+*/
+
+bool QtSingleApplication::isRunning()
+{
+    return peer->isClient();
+}
+
+
+/*!
+    Tries to send the text \a message to the currently running
+    instance. The QtSingleApplication object in the running instance
+    will emit the messageReceived() signal when it receives the
+    message.
+
+    This function returns true if the message has been sent to, and
+    processed by, the current instance. If there is no instance
+    currently running, or if the running instance fails to process the
+    message within \a timeout milliseconds, this function return false.
+
+    \sa isRunning(), messageReceived()
+*/
+bool QtSingleApplication::sendMessage(const QString &message, int timeout)
+{
+    return peer->sendMessage(message, timeout);
+}
+
+
+/*!
+    Returns the application identifier. Two processes with the same
+    identifier will be regarded as instances of the same application.
+*/
+QString QtSingleApplication::id() const
+{
+    return peer->applicationId();
+}
+
+
+/*!
+  Sets the activation window of this application to \a aw. The
+  activation window is the widget that will be activated by
+  activateWindow(). This is typically the application's main window.
+
+  If \a activateOnMessage is true (the default), the window will be
+  activated automatically every time a message is received, just prior
+  to the messageReceived() signal being emitted.
+
+  \sa activateWindow(), messageReceived()
+*/
+
+void QtSingleApplication::setActivationWindow(QWidget* aw, bool activateOnMessage)
+{
+    actWin = aw;
+    if (activateOnMessage)
+        connect(peer, SIGNAL(messageReceived(const QString&)), this, SLOT(activateWindow()));
+    else
+        disconnect(peer, SIGNAL(messageReceived(const QString&)), this, SLOT(activateWindow()));
+}
+
+
+/*!
+    Returns the applications activation window if one has been set by
+    calling setActivationWindow(), otherwise returns 0.
+
+    \sa setActivationWindow()
+*/
+QWidget* QtSingleApplication::activationWindow() const
+{
+    return actWin;
+}
+
+
+/*!
+  De-minimizes, raises, and activates this application's activation window.
+  This function does nothing if no activation window has been set.
+
+  This is a convenience function to show the user that this
+  application instance has been activated when he has tried to start
+  another instance.
+
+  This function should typically be called in response to the
+  messageReceived() signal. By default, that will happen
+  automatically, if an activation window has been set.
+
+  \sa setActivationWindow(), messageReceived(), initialize()
+*/
+void QtSingleApplication::activateWindow()
+{
+    if (actWin) {
+        actWin->setWindowState(actWin->windowState() & ~Qt::WindowMinimized);
+        actWin->raise();
+        actWin->activateWindow();
+    }
+}
+
+
+/*!
+    \fn void QtSingleApplication::messageReceived(const QString& message)
+
+    This signal is emitted when the current instance receives a \a
+    message from another instance of this application.
+
+    \sa sendMessage(), setActivationWindow(), activateWindow()
+*/
+
+
+/*!
+    \fn void QtSingleApplication::initialize(bool dummy = true)
+
+    \obsolete
+*/

src/qtsingleapp/qtsingleapplication.h

@@ -0,0 +1,105 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+
+#include <QtGui/QApplication>
+
+class QtLocalPeer;
+
+#if defined(Q_WS_WIN)
+#  if !defined(QT_QTSINGLEAPPLICATION_EXPORT) && !defined(QT_QTSINGLEAPPLICATION_IMPORT)
+#    define QT_QTSINGLEAPPLICATION_EXPORT
+#  elif defined(QT_QTSINGLEAPPLICATION_IMPORT)
+#    if defined(QT_QTSINGLEAPPLICATION_EXPORT)
+#      undef QT_QTSINGLEAPPLICATION_EXPORT
+#    endif
+#    define QT_QTSINGLEAPPLICATION_EXPORT __declspec(dllimport)
+#  elif defined(QT_QTSINGLEAPPLICATION_EXPORT)
+#    undef QT_QTSINGLEAPPLICATION_EXPORT
+#    define QT_QTSINGLEAPPLICATION_EXPORT __declspec(dllexport)
+#  endif
+#else
+#  define QT_QTSINGLEAPPLICATION_EXPORT
+#endif
+
+class QT_QTSINGLEAPPLICATION_EXPORT QtSingleApplication : public QApplication
+{
+    Q_OBJECT
+
+public:
+    QtSingleApplication(int &argc, char **argv, bool GUIenabled = true);
+    QtSingleApplication(const QString &id, int &argc, char **argv);
+    QtSingleApplication(int &argc, char **argv, Type type);
+#if defined(Q_WS_X11)
+    QtSingleApplication(Display* dpy, Qt::HANDLE visual = 0, Qt::HANDLE colormap = 0);
+    QtSingleApplication(Display *dpy, int &argc, char **argv, Qt::HANDLE visual = 0, Qt::HANDLE cmap= 0);
+    QtSingleApplication(Display* dpy, const QString &appId, int argc, char **argv, Qt::HANDLE visual = 0, Qt::HANDLE colormap = 0);
+#endif
+
+    bool isRunning();
+    QString id() const;
+
+    void setActivationWindow(QWidget* aw, bool activateOnMessage = true);
+    QWidget* activationWindow() const;
+
+    // Obsolete:
+    void initialize(bool dummy = true)
+        { isRunning(); Q_UNUSED(dummy) }
+
+public Q_SLOTS:
+    bool sendMessage(const QString &message, int timeout = 5000);
+    void activateWindow();
+
+
+Q_SIGNALS:
+    void messageReceived(const QString &message);
+
+
+private:
+    void sysInit(const QString &appId = QString());
+    QtLocalPeer *peer;
+    QWidget *actWin;
+};

src/qtsingleapp/qtsingleapplication.pri

@@ -0,0 +1,16 @@
+include(../common.pri)
+INCLUDEPATH += $$PWD
+DEPENDPATH += $$PWD
+QT *= network
+
+qtsingleapplication-uselib:!qtsingleapplication-buildlib {
+    LIBS += -L$$QTSINGLEAPPLICATION_LIBDIR -l$$QTSINGLEAPPLICATION_LIBNAME
+} else {
+    SOURCES += $$PWD/qtsingleapplication.cpp $$PWD/qtlocalpeer.cpp
+    HEADERS += $$PWD/qtsingleapplication.h $$PWD/qtlocalpeer.h
+}
+
+win32 {
+    contains(TEMPLATE, lib):contains(CONFIG, shared):DEFINES += QT_QTSINGLEAPPLICATION_EXPORT
+    else:qtsingleapplication-uselib:DEFINES += QT_QTSINGLEAPPLICATION_IMPORT
+}

src/qtsingleapp/qtsinglecoreapplication.cpp

@@ -0,0 +1,155 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+
+#include "qtsinglecoreapplication.h"
+#include "qtlocalpeer.h"
+
+/*!
+    \class QtSingleCoreApplication qtsinglecoreapplication.h
+    \brief A variant of the QtSingleApplication class for non-GUI applications.
+
+    This class is a variant of QtSingleApplication suited for use in
+    console (non-GUI) applications. It is an extension of
+    QCoreApplication (instead of QApplication). It does not require
+    the QtGui library.
+
+    The API and usage is identical to QtSingleApplication, except that
+    functions relating to the "activation window" are not present, for
+    obvious reasons. Please refer to the QtSingleApplication
+    documentation for explanation of the usage.
+
+    A QtSingleCoreApplication instance can communicate to a
+    QtSingleApplication instance if they share the same application
+    id. Hence, this class can be used to create a light-weight
+    command-line tool that sends commands to a GUI application.
+
+    \sa QtSingleApplication
+*/
+
+/*!
+    Creates a QtSingleCoreApplication object. The application identifier
+    will be QCoreApplication::applicationFilePath(). \a argc and \a
+    argv are passed on to the QCoreAppliation constructor.
+*/
+
+QtSingleCoreApplication::QtSingleCoreApplication(int &argc, char **argv)
+    : QCoreApplication(argc, argv)
+{
+    peer = new QtLocalPeer(this);
+    connect(peer, SIGNAL(messageReceived(const QString&)), SIGNAL(messageReceived(const QString&)));
+}
+
+
+/*!
+    Creates a QtSingleCoreApplication object with the application
+    identifier \a appId. \a argc and \a argv are passed on to the
+    QCoreAppliation constructor.
+*/
+QtSingleCoreApplication::QtSingleCoreApplication(const QString &appId, int &argc, char **argv)
+    : QCoreApplication(argc, argv)
+{
+    peer = new QtLocalPeer(this, appId);
+    connect(peer, SIGNAL(messageReceived(const QString&)), SIGNAL(messageReceived(const QString&)));
+}
+
+
+/*!
+    Returns true if another instance of this application is running;
+    otherwise false.
+
+    This function does not find instances of this application that are
+    being run by a different user (on Windows: that are running in
+    another session).
+
+    \sa sendMessage()
+*/
+
+bool QtSingleCoreApplication::isRunning()
+{
+    return peer->isClient();
+}
+
+
+/*!
+    Tries to send the text \a message to the currently running
+    instance. The QtSingleCoreApplication object in the running instance
+    will emit the messageReceived() signal when it receives the
+    message.
+
+    This function returns true if the message has been sent to, and
+    processed by, the current instance. If there is no instance
+    currently running, or if the running instance fails to process the
+    message within \a timeout milliseconds, this function return false.
+
+    \sa isRunning(), messageReceived()
+*/
+
+bool QtSingleCoreApplication::sendMessage(const QString &message, int timeout)
+{
+    return peer->sendMessage(message, timeout);
+}
+
+
+/*!
+    Returns the application identifier. Two processes with the same
+    identifier will be regarded as instances of the same application.
+*/
+
+QString QtSingleCoreApplication::id() const
+{
+    return peer->applicationId();
+}
+
+
+/*!
+    \fn void QtSingleCoreApplication::messageReceived(const QString& message)
+
+    This signal is emitted when the current instance receives a \a
+    message from another instance of this application.
+
+    \sa sendMessage()
+*/

src/qtsingleapp/qtsinglecoreapplication.h

@@ -0,0 +1,73 @@
+/****************************************************************************
+** 
+** Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+** 
+** This file is part of a Qt Solutions component.
+**
+** Commercial Usage  
+** Licensees holding valid Qt Commercial licenses may use this file in
+** accordance with the Qt Solutions Commercial License Agreement provided
+** with the Software or, alternatively, in accordance with the terms
+** contained in a written agreement between you and Nokia.
+** 
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+** 
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
+** package.
+** 
+** GNU General Public License Usage 
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+** 
+** Please note Third Party Software included with Qt Solutions may impose
+** additional restrictions and it is the user's responsibility to ensure
+** that they have met the licensing requirements of the GPL, LGPL, or Qt
+** Solutions Commercial license and the relevant license of the Third
+** Party Software they are using.
+** 
+** If you are unsure which license is appropriate for your use, please
+** contact Nokia at qt-info@nokia.com.
+** 
+****************************************************************************/
+
+
+#include <QtCore/QCoreApplication>
+
+class QtLocalPeer;
+
+class QtSingleCoreApplication : public QCoreApplication
+{
+    Q_OBJECT
+
+public:
+    QtSingleCoreApplication(int &argc, char **argv);
+    QtSingleCoreApplication(const QString &id, int &argc, char **argv);
+
+    bool isRunning();
+    QString id() const;
+
+public Q_SLOTS:
+    bool sendMessage(const QString &message, int timeout = 5000);
+
+
+Q_SIGNALS:
+    void messageReceived(const QString &message);
+
+
+private:
+    QtLocalPeer* peer;
+};

src/qtsingleapp/qtsinglecoreapplication.pri

@@ -0,0 +1,10 @@
+INCLUDEPATH	+= $$PWD
+DEPENDPATH      += $$PWD
+HEADERS		+= $$PWD/qtsinglecoreapplication.h $$PWD/qtlocalpeer.h
+SOURCES		+= $$PWD/qtsinglecoreapplication.cpp $$PWD/qtlocalpeer.cpp
+
+QT *= network
+
+win32:contains(TEMPLATE, lib):contains(CONFIG, shared) {
+    DEFINES += QT_QTSINGLECOREAPPLICATION_EXPORT=__declspec(dllexport)
+}

src/src.pro

@@ -319,6 +319,12 @@ contains(DEFINES, DISABLE_GUI) {
   }
 }
 
+contains(DEFINES, DISABLE_GUI) {
+  include(qtsingleapp/qtsinglecoreapplication.pri)
+} else {
+  include(qtsingleapp/qtsingleapplication.pri)
+}
+
 !contains(DEFINES, DISABLE_GUI) {
   FORMS += ui/mainwindow.ui \
            ui/options.ui \
@@ -371,7 +377,7 @@ SOURCES += main.cpp \
              trackerlist.cpp
 
   macx {
-    HEADERS += qmacapplication.cpp
+    SOURCES += qmacapplication.cpp
   }
 }