Add JettingProxy relay, convert Xpl2Client to active connection modelHEADmaster

Insert a transparent TCP proxy between the controller and N clients:
- JettingProxy listens on 9110-9112 (controller) and 9210-9212 (clients)
- Broadcasts controller frames to all clients, forwards client→controller
- Independent KA_PING handling on both sides

Convert Xpl2Client from passive QTcpServer listener to active QTcpSocket
outbound connections with auto-retry. New QML API: host/commandPort
properties, connectToProxy()/disconnectFromProxy() replacing
startListening()/stopListening().

1 files changed, 54 insertions, 0 deletions

diff --git a/jetting-proxy/JettingProxy.h b/jetting-proxy/JettingProxy.h
new file mode 100644
index 0000000..ec8c26d
--- /dev/null
+++ b/jetting-proxy/JettingProxy.h
@@ -0,0 +1,54 @@
+/**
+ * @file   JettingProxy.h
+ * @brief  Transparent TCP relay between one controller and N clients.
+ */
+#pragma once
+
+#include <QList>
+#include <QObject>
+#include <QTcpServer>
+#include <QTcpSocket>
+#include <QTimer>
+
+class JettingProxy : public QObject
+{
+  Q_OBJECT
+
+public:
+  explicit JettingProxy (quint16 controllerPortBase, quint16 clientPortBase,
+                         QObject *parent = nullptr);
+  static void enableWireDebug ();
+
+private slots:
+  void onControllerConnected ();
+  void onControllerDisconnected ();
+  void onControllerDataReady ();
+  void onClientConnected ();
+  void onClientDisconnected ();
+  void onClientDataReady ();
+  /* Send KA_PING to all connected clients on all channels. */
+  void tick ();
+
+private:
+  struct Channel
+  {
+    const char *name = nullptr;
+    QTcpServer controllerServer;
+    QTcpSocket *controllerSocket = nullptr;
+    QTcpServer clientServer;
+    QList<QTcpSocket *> clientSockets;
+  };
+
+  void setupChannel (Channel &channel, const char *name,
+                     quint16 controllerPort, quint16 clientPort);
+  Channel *channelForControllerServer (QTcpServer *server);
+  Channel *channelForControllerSocket (QTcpSocket *socket);
+  Channel *channelForClientSocket (QTcpSocket *socket);
+  QString logTag (const Channel &channel) const;
+
+  Channel m_command;
+  Channel m_imaging;
+  Channel m_status;
+  QTimer m_tickTimer;
+  static bool s_wireDebug;
+};