Introduce a 'change listen port' cmd option

Closes #17789.
PR #17862.

src/app/application.cpp

@@ -196,6 +196,12 @@ Application::Application(int &argc, char **argv)
 
     if (m_commandLineArgs.webUiPort > 0) // it will be -1 when user did not set any value
         Preferences::instance()->setWebUiPort(m_commandLineArgs.webUiPort);
+
+    if (m_commandLineArgs.torrentingPort > 0) // it will be -1 when user did not set any value
+    {
+        SettingValue<int> port {u"BitTorrent/Session/Port"_qs};
+        port = m_commandLineArgs.torrentingPort;
+    }
 }
 
 Application::~Application()

src/app/cmdoptions.cpp

@@ -326,6 +326,7 @@ namespace
     constexpr const BoolOption NO_SPLASH_OPTION {"no-splash"};
 #endif
     constexpr const IntOption WEBUI_PORT_OPTION {"webui-port"};
+    constexpr const IntOption TORRENTING_PORT_OPTION {"torrenting-port"};
     constexpr const StringOption PROFILE_OPTION {"profile"};
     constexpr const StringOption CONFIGURATION_OPTION {"configuration"};
     constexpr const BoolOption RELATIVE_FASTRESUME {"relative-fastresume"};
@@ -353,6 +354,7 @@ QBtCommandLineParameters::QBtCommandLineParameters(const QProcessEnvironment &en
     , shouldDaemonize(DAEMON_OPTION.value(env))
 #endif
     , webUiPort(WEBUI_PORT_OPTION.value(env, -1))
+    , torrentingPort(TORRENTING_PORT_OPTION.value(env, -1))
     , addPaused(PAUSED_OPTION.value(env))
     , skipDialog(SKIP_DIALOG_OPTION.value(env))
     , profileDir(PROFILE_OPTION.value(env))
@@ -427,6 +429,15 @@ QBtCommandLineParameters parseCommandLine(const QStringList &args)
                     throw CommandLineParameterError(QObject::tr("%1 must specify a valid port (1 to 65535).")
                                                     .arg(u"--webui-port"_qs));
             }
+            else if (arg == TORRENTING_PORT_OPTION)
+            {
+                result.torrentingPort = TORRENTING_PORT_OPTION.value(arg);
+                if ((result.torrentingPort < 1) || (result.torrentingPort > 65535))
+                {
+                    throw CommandLineParameterError(QObject::tr("%1 must specify a valid port (1 to 65535).")
+                                                    .arg(u"--torrenting-port"_qs));
+                }
+            }
 #ifndef DISABLE_GUI
             else if (arg == NO_SPLASH_OPTION)
             {
@@ -537,6 +548,9 @@ QString makeUsage(const QString &prgName)
         + WEBUI_PORT_OPTION.usage(QObject::tr("port"))
         + wrapText(QObject::tr("Change the Web UI port"))
         + u'\n'
+        + TORRENTING_PORT_OPTION.usage(QObject::tr("port"))
+        + wrapText(QObject::tr("Change the torrenting port"))
+        + u'\n'
 #ifndef DISABLE_GUI
         + NO_SPLASH_OPTION.usage() + wrapText(QObject::tr("Disable splash screen")) + u'\n'
 #elif !defined(Q_OS_WIN)

src/app/cmdoptions.h

@@ -56,6 +56,7 @@ struct QBtCommandLineParameters
     bool shouldDaemonize;
 #endif
     int webUiPort;
+    int torrentingPort;
     std::optional<bool> addPaused;
     std::optional<bool> skipDialog;
     QStringList torrents;