diff --git a/src/gui/Application.cpp b/src/gui/Application.cpp
index 432525ad6..fc14bafb3 100644
--- a/src/gui/Application.cpp
+++ b/src/gui/Application.cpp
@@ -49,6 +49,13 @@ namespace
     int g_OriginalFontSize = 0;
 } // namespace
 
+enum Application::SocketCmd : quint32
+{
+    OpenFiles = 1,
+    LockAll,
+    Unlock,
+};
+
 Application::Application(int& argc, char** argv)
     : QApplication(argc, argv)
 #ifdef Q_OS_UNIX
@@ -56,11 +63,7 @@ Application::Application(int& argc, char** argv)
 #endif
     , m_alreadyRunning(false)
     , m_lockFile(nullptr)
-#if defined(Q_OS_WIN) || (defined(Q_OS_UNIX) && !defined(Q_OS_MACOS))
 {
-#else
-{
-#endif
 #if defined(Q_OS_UNIX)
     registerUnixSignals();
 #endif
@@ -324,13 +327,12 @@ void Application::socketReadyRead()
         return;
     }
 
-    QStringList fileNames;
-    quint32 id;
+    SocketCmd id;
     in >> id;
 
-    // TODO: move constants to enum
     switch (id) {
-    case 1:
+    case SocketCmd::OpenFiles: {
+        QStringList fileNames;
         in >> fileNames;
         for (const QString& fileName : asConst(fileNames)) {
             const QFileInfo fInfo(fileName);
@@ -338,11 +340,16 @@ void Application::socketReadyRead()
                 emit openFile(fileName);
             }
         }
-
         break;
-    case 2:
+    }
+    case SocketCmd::LockAll:
         getMainWindow()->lockAllDatabases();
         break;
+    case SocketCmd::Unlock:
+        QString filename, password, keyfile;
+        in >> filename >> password >> keyfile;
+        emit openFile(filename, password, keyfile);
+        break;
     }
 
     socket->deleteLater();
@@ -350,20 +357,10 @@ void Application::socketReadyRead()
 
 bool Application::isAlreadyRunning() const
 {
-#ifdef QT_DEBUG
-    // In DEBUG mode we can run unlimited instances
-    return false;
-#endif
     return config()->get(Config::SingleInstance).toBool() && m_alreadyRunning;
 }
 
-/**
- * Send to-open file names to the running UI instance
- *
- * @param fileNames - list of file names to open
- * @return true if all operations succeeded (connection made, data sent, connection closed)
- */
-bool Application::sendFileNamesToRunningInstance(const QStringList& fileNames)
+bool Application::sendSocketCommand(SocketCmd id, const std::function<void(QDataStream&)>& caller)
 {
     QLocalSocket client;
     client.connectToServer(m_socketName);
@@ -376,8 +373,8 @@ bool Application::sendFileNamesToRunningInstance(const QStringList& fileNames)
     QDataStream out(&data, QIODevice::WriteOnly);
     out.setVersion(QDataStream::Qt_5_0);
     out << quint32(0); // reserve space for block size
-    out << quint32(1); // ID for file name send. TODO: move to enum
-    out << fileNames; // send file names to be opened
+    out << id; // ID of command being sent.
+    caller(out); // Pass to caller to add any additional data
     out.device()->seek(0);
     out << quint32(data.size() - sizeof(quint32)); // replace the previous constant 0 with block size
 
@@ -388,6 +385,17 @@ bool Application::sendFileNamesToRunningInstance(const QStringList& fileNames)
     return writeOk && disconnected;
 }
 
+/**
+ * Send to-open file names to the running UI instance
+ *
+ * @param fileNames - list of file names to open
+ * @return true if all operations succeeded (connection made, data sent, connection closed)
+ */
+bool Application::sendFileNamesToRunningInstance(const QStringList& fileNames)
+{
+    return this->sendSocketCommand(SocketCmd::OpenFiles, [&](QDataStream& out) { out << fileNames; });
+}
+
 /**
  * Locks all open databases in the running instance
  *
@@ -395,29 +403,18 @@ bool Application::sendFileNamesToRunningInstance(const QStringList& fileNames)
  */
 bool Application::sendLockToInstance()
 {
-    // Make a connection to avoid SIGSEGV
-    QLocalSocket client;
-    client.connectToServer(m_socketName);
-    const bool connected = client.waitForConnected(WaitTimeoutMSec);
-    if (!connected) {
-        return false;
-    }
+    return this->sendSocketCommand(SocketCmd::LockAll, [](QDataStream&) { /* No Data */ });
+}
 
-    // Send lock signal
-    QByteArray data;
-    QDataStream out(&data, QIODevice::WriteOnly);
-    out.setVersion(QDataStream::Qt_5_0);
-    out << quint32(0); // reserve space for block size
-    out << quint32(2); // ID for database lock. TODO: move to enum
-    out.device()->seek(0);
-    out << quint32(data.size() - sizeof(quint32)); // replace the previous constant 0 with block size
-
-    // Finish gracefully
-    const bool writeOk = client.write(data) != -1 && client.waitForBytesWritten(WaitTimeoutMSec);
-    client.disconnectFromServer();
-    const bool disconnected =
-        client.state() == QLocalSocket::UnconnectedState || client.waitForConnected(WaitTimeoutMSec);
-    return writeOk && disconnected;
+/**
+ * Open and unlock a database file in the running instance
+ *
+ * @return true if the instance receives the request
+ */
+bool Application::sendUnlockToInstance(const QString& filename, const QString& password, const QString& keyfile)
+{
+    return this->sendSocketCommand(SocketCmd::Unlock,
+                                   [&](QDataStream& out) { out << filename << password << keyfile; });
 }
 
 bool Application::isDarkTheme() const
diff --git a/src/gui/Application.h b/src/gui/Application.h
index 349c93923..b00f8ce99 100644
--- a/src/gui/Application.h
+++ b/src/gui/Application.h
@@ -23,6 +23,7 @@
 #include <QApplication>
 #include <QString>
 #include <QtNetwork/qlocalserver.h>
+#include <functional>
 
 #if defined(Q_OS_WIN) || (defined(Q_OS_UNIX) && !defined(Q_OS_MACOS))
 
@@ -52,11 +53,12 @@ public:
 
     bool sendFileNamesToRunningInstance(const QStringList& fileNames);
     bool sendLockToInstance();
+    bool sendUnlockToInstance(const QString& filename, const QString& password = {}, const QString& keyfile = {});
 
     void restart();
 
 signals:
-    void openFile(const QString& filename);
+    void openFile(const QString& filename, const QString& password = {}, const QString& keyfile = {});
     void anotherInstanceStarted();
     void applicationActivated();
     void quitSignalReceived();
@@ -78,6 +80,10 @@ private:
     static void handleUnixSignal(int sig);
     static int unixSignalSocket[2];
 #endif
+
+    enum SocketCmd : quint32;
+    bool sendSocketCommand(SocketCmd id, const std::function<void(QDataStream&)>&);
+
     bool m_alreadyRunning;
     bool m_darkTheme = false;
     QLockFile* m_lockFile;
diff --git a/src/gui/MainWindow.cpp b/src/gui/MainWindow.cpp
index 25b96c5ae..6ccd759ab 100644
--- a/src/gui/MainWindow.cpp
+++ b/src/gui/MainWindow.cpp
@@ -671,8 +671,8 @@ MainWindow::MainWindow()
 
     connect(qApp, SIGNAL(anotherInstanceStarted()), this, SLOT(bringToFront()));
     connect(qApp, SIGNAL(applicationActivated()), this, SLOT(bringToFront()));
-    connect(qApp, SIGNAL(openFile(QString)), this, SLOT(openDatabase(QString)));
     connect(qApp, SIGNAL(quitSignalReceived()), this, SLOT(appExit()), Qt::DirectConnection);
+    connect(static_cast<Application*>(qApp), &Application::openFile, this, &MainWindow::openDatabase);
 
     // Setup the status bar
     statusBar()->setFixedHeight(24);
diff --git a/src/main.cpp b/src/main.cpp
index 2c4da4c1f..f9af22ecc 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -49,6 +49,18 @@ Q_IMPORT_PLUGIN(QXcbIntegrationPlugin)
 #include <windows.h>
 #endif
 
+namespace
+{
+    QString promptPassword()
+    {
+        // we always need consume a line of STDIN if --pw-stdin is set to clear out the
+        // buffer for native messaging, even if the specified file does not exist
+        QTextStream out(stdout, QIODevice::WriteOnly);
+        out << QObject::tr("Database password: ") << Qt::flush;
+        return Utils::getPassword();
+    }
+} // namespace
+
 int main(int argc, char** argv)
 {
     QT_REQUIRE_VERSION(argc, argv, QT_VERSION_STR)
@@ -140,9 +152,14 @@ int main(int argc, char** argv)
         }
     }
 #endif
+    Utils::setDefaultTextStreams();
+
+    const bool pwstdin = parser.isSet(pwstdinOption);
+    const QString keyfile = parser.value(keyfileOption);
 
     // Process single instance and early exit if already running
     if (app.isAlreadyRunning()) {
+        qWarning() << QObject::tr("Another instance of KeePassXC is already running.").toUtf8().constData();
         if (parser.isSet(lockOption)) {
             if (app.sendLockToInstance()) {
                 qInfo() << QObject::tr("Databases have been locked.").toUtf8().constData();
@@ -151,11 +168,13 @@ int main(int argc, char** argv)
                 return EXIT_FAILURE;
             }
         } else {
-            if (!fileNames.isEmpty()) {
-                app.sendFileNamesToRunningInstance(fileNames);
+            for (const QString& filename : fileNames) {
+                QString password;
+                if (pwstdin) {
+                    password = promptPassword();
+                }
+                app.sendUnlockToInstance(filename, password, keyfile);
             }
-
-            qWarning() << QObject::tr("Another instance of KeePassXC is already running.").toUtf8().constData();
         }
         return EXIT_SUCCESS;
     }
@@ -176,8 +195,6 @@ int main(int argc, char** argv)
         return EXIT_FAILURE;
     }
 
-    Utils::setDefaultTextStreams();
-
     // Apply the configured theme before creating any GUI elements
     app.applyTheme();
 
@@ -195,17 +212,12 @@ int main(int argc, char** argv)
     // This ensures any top-level windows (Main Window, Modal Dialogs, etc.) are excluded from screenshots
     mainWindow.setAllowScreenCapture(parser.isSet(allowScreenCaptureOption));
 
-    const bool pwstdin = parser.isSet(pwstdinOption);
     for (const QString& filename : fileNames) {
         QString password;
         if (pwstdin) {
-            // we always need consume a line of STDIN if --pw-stdin is set to clear out the
-            // buffer for native messaging, even if the specified file does not exist
-            QTextStream out(stdout, QIODevice::WriteOnly);
-            out << QObject::tr("Database password: ") << Qt::flush;
-            password = Utils::getPassword();
+            password = promptPassword();
         }
-        mainWindow.openDatabase(filename, password, parser.value(keyfileOption));
+        mainWindow.openDatabase(filename, password, keyfile);
     }
 
     // start minimized if configured