Detect running server on startup

src/SimulationRunner.cc

@@ -192,6 +192,14 @@ SimulationRunner::SimulationRunner(const sdf::World &_world,
 
   this->node = std::make_unique<transport::Node>(opts);
 
+  std::vector<transport::MessagePublisher> pubs;
+  std::vector<transport::MessagePublisher> subs;
+  this->node->TopicInfo("/world/" + this->worldName + "/stats", pubs, subs);
+  if (!pubs.empty())
+  {
+    gzerr << "Another world of the same name is running" << std::endl;
+  }
+
   // Create the system manager
   this->systemMgr = std::make_unique<SystemManager>(
       _systemLoader, &this->entityCompMgr, &this->eventMgr, validNs,

src/gui/QuickStartHandler.cc

@@ -18,10 +18,27 @@
 #include "QuickStartHandler.hh"
 
 #include "gz/sim/InstallationDirectories.hh"
+#include <gz/transport/Node.hh>
+#include <gz/common/Console.hh>
 
 using namespace gz;
 using namespace sim::gui;
 
+QuickStartHandler::QuickStartHandler()
+{
+  // Create the node if needed
+  this->node = std::make_unique<gz::transport::Node>();
+
+  std::vector<transport::MessagePublisher> publishers;
+  std::vector<transport::MessagePublisher> subscribers;
+  this->node->TopicInfo("/stats", publishers, subscribers);
+  if (!publishers.empty())
+  {
+    gzwarn << "Detected an already running world on start" << std::endl;
+    return;
+  }
+}
+
 /////////////////////////////////////////////////
 QString QuickStartHandler::WorldsPath() const
 {

src/gui/QuickStartHandler.hh

@@ -23,6 +23,12 @@
 #include "gz/sim/config.hh"
 #include "gz/sim/gui/Export.hh"
 
+#include <gz/transport/Node.hh>
+#include <gz/common/Console.hh>
+
+#include <memory>
+#include <vector>
+
 namespace gz
 {
 namespace sim
@@ -36,6 +42,9 @@ class GZ_SIM_GUI_VISIBLE QuickStartHandler : public QObject
 {
   Q_OBJECT
 
+  // Explicitly declare the constructor
+  public: QuickStartHandler();
+
   /// \brief Get worlds path
   /// \return worlds directory path
   public: Q_INVOKABLE QString WorldsPath() const;
@@ -69,6 +78,9 @@ class GZ_SIM_GUI_VISIBLE QuickStartHandler : public QObject
 
   /// \brief Get starting world url.
   private: std::string startingWorld{""};
+
+  // Add a member for the transport node
+  private: std::unique_ptr<gz::transport::Node> node;
 };
 }
 }