XPL2 protocol foundation: wire framing, typed API, KA_PING, GS_JC_VERSION

Add Xpl2Protocol namespace with buildMessage/parseMessage for wire
serialization. Replace raw send/receive API on Xpl2Client with typed
protocol methods and internal dispatch. Auto-reply to KA_PING on all
sockets (qDebug only). Add GS_JC_VERSION as first typed command with
controllerId, firmwareVersion, hardwareVersion, printheadCount properties.

Upgrade mock server from echo to line-based command dispatch with 1s
KA_PING timer and canned GS_JC_VERSION response. Unknown commands
produce qWarning instead of echo.

Overhaul demo: remove raw send UI and port config, add wireDebug
toggle and Get JC Version button.

1 files changed, 54 insertions, 7 deletions

diff --git a/mock-server/EchoServer.cpp b/mock-server/EchoServer.cpp
index 43fc6f9..8d86df1 100644
--- a/mock-server/EchoServer.cpp
+++ b/mock-server/EchoServer.cpp
@@ -1,6 +1,6 @@
 /**
  * @file   EchoServer.cpp
- * @brief  Simple TCP echo server for a single port.
+ * @brief  Mock XPL2 server for a single port.
  */
 #include "EchoServer.h"
 
@@ -12,11 +12,16 @@ EchoServer::EchoServer (quint16 port, const char *name, QObject *parent)
   connect (this, &QTcpServer::newConnection, this,
            &EchoServer::onNewConnection);
 
+  connect (&m_pingTimer, &QTimer::timeout, this, &EchoServer::sendKaPing);
+
   if (!listen (QHostAddress::Any, port))
     qCritical ("Failed to listen on %s port %d: %s", m_name, m_port,
                qPrintable (errorString ()));
   else
-    qInfo ("Listening on %s port %d", m_name, m_port);
+    {
+      qInfo ("Listening on %s port %d", m_name, m_port);
+      m_pingTimer.start (1000);
+    }
 }
 
 void
@@ -25,20 +30,23 @@ EchoServer::onNewConnection ()
   while (auto *sock = nextPendingConnection ())
     {
       qInfo ("[%s:%d] client connected", m_name, m_port);
+      m_clients.append (sock);
       connect (sock, &QTcpSocket::readyRead, this,
-               &EchoServer::onClientReadyRead);
+               &EchoServer::onClientMessageReady);
       connect (sock, &QTcpSocket::disconnected, this,
                &EchoServer::onClientDisconnected);
     }
 }
 
 void
-EchoServer::onClientReadyRead ()
+EchoServer::onClientMessageReady ()
 {
   auto *sock = qobject_cast<QTcpSocket *> (sender ());
-  QByteArray data = sock->readAll ();
-  qInfo ("[%s:%d] echo %lld bytes", m_name, m_port, data.size ());
-  sock->write (data);
+  while (sock->canReadLine ())
+    {
+      QByteArray line = sock->readLine ();
+      handleCommand (sock, line);
+    }
 }
 
 void
@@ -46,5 +54,44 @@ EchoServer::onClientDisconnected ()
 {
   auto *sock = qobject_cast<QTcpSocket *> (sender ());
   qInfo ("[%s:%d] client disconnected", m_name, m_port);
+  m_clients.removeOne (sock);
   sock->deleteLater ();
 }
+
+void
+EchoServer::sendKaPing ()
+{
+  for (auto *client : m_clients)
+    {
+      if (client->state () == QAbstractSocket::ConnectedState)
+        client->write ("KA_PING\n");
+    }
+}
+
+void
+EchoServer::handleCommand (QTcpSocket *client, const QByteArray &line)
+{
+  QByteArray trimmed = line.trimmed ();
+  if (trimmed.isEmpty ())
+    return;
+
+  /* Split on first comma to get command token. */
+  int comma = trimmed.indexOf (',');
+  QByteArray cmd = (comma >= 0) ? trimmed.left (comma) : trimmed;
+
+  if (cmd == "KA_PING")
+    {
+      qDebug ("[%s:%d] KA_PING ACK received", m_name, m_port);
+      return;
+    }
+
+  if (cmd == "GS_JC_VERSION")
+    {
+      qInfo ("[%s:%d] -> GS_JC_VERSION reply", m_name, m_port);
+      client->write ("GS_JC_VERSION,1,\"1.05\",\"2.00\",15\n");
+      return;
+    }
+
+  qWarning ("[%s:%d] Unknown command: %s", m_name, m_port,
+            trimmed.constData ());
+}