Invert TCP connection model: client listens, server connects

The XPL2 protocol specifies that the JI2 controller initiates connections
to the client, not the other way around. Xpl2Client now listens on 3 ports
via QTcpServer and accepts inbound connections; MockServer connects out
with auto-retry on the 1s KA_PING tick.

QML API: startListening/stopListening, listening+connected properties,
host property removed. Mock server gains --host CLI arg.

1 files changed, 132 insertions, 72 deletions

diff --git a/src/Xpl2Client.cpp b/src/Xpl2Client.cpp
index d3a6da2..4fa502e 100644
--- a/src/Xpl2Client.cpp
+++ b/src/Xpl2Client.cpp
@@ -5,6 +5,7 @@
 #include "Xpl2Client.h"
 
 #include <QDebug>
+#include <QTcpSocket>
 
 bool Xpl2Client::s_wireDebug = false;
 
@@ -157,36 +158,19 @@ Xpl2Client::s_responseTable = {
 
 Xpl2Client::Xpl2Client (QObject *parent) : QObject (parent)
 {
-  for (auto *socket : { &m_commandSocket, &m_imagingSocket, &m_statusSocket })
-    {
-      connect (socket, &QTcpSocket::connected, this,
-               &Xpl2Client::onSocketConnected);
-      connect (socket, &QTcpSocket::disconnected, this,
-               &Xpl2Client::onSocketDisconnected);
-      connect (socket, &QTcpSocket::readyRead, this,
-               &Xpl2Client::onSocketMessageReady);
-      connect (socket, &QAbstractSocket::errorOccurred, this,
-               &Xpl2Client::onSocketError);
-    }
+  setupServer (m_commandServer, m_commandPort);
+  setupServer (m_imagingServer, m_imagingPort);
+  setupServer (m_statusServer, m_statusPort);
 }
 
 /* ------------------------------------------------------------------ */
 /*  Properties                                                        */
 /* ------------------------------------------------------------------ */
 
-QString
-Xpl2Client::host () const
-{
-  return m_host;
-}
-
-void
-Xpl2Client::setHost (const QString &host)
+bool
+Xpl2Client::isListening () const
 {
-  if (m_host == host)
-    return;
-  m_host = host;
-  emit hostChanged ();
+  return m_listening;
 }
 
 bool
@@ -230,25 +214,78 @@ Xpl2Client::enableWireDebug ()
 /* ------------------------------------------------------------------ */
 
 void
-Xpl2Client::connectToServer ()
+Xpl2Client::setupServer (QTcpServer &server, quint16 port)
+{
+  Q_UNUSED (port)
+  connect (&server, &QTcpServer::newConnection, this,
+           &Xpl2Client::onNewConnection);
+}
+
+void
+Xpl2Client::startListening ()
 {
-  if (m_connected)
+  if (m_listening)
     {
-      emit statusMessage (QStringLiteral ("Already connected"));
+      emit statusMessage (QStringLiteral ("Already listening"));
       return;
     }
-  emit statusMessage (QStringLiteral ("Connecting to %1…").arg (m_host));
-  m_commandSocket.connectToHost (m_host, m_commandPort);
-  m_imagingSocket.connectToHost (m_host, m_imagingPort);
-  m_statusSocket.connectToHost (m_host, m_statusPort);
+  if (!m_commandServer.listen (QHostAddress::Any, m_commandPort)
+      || !m_imagingServer.listen (QHostAddress::Any, m_imagingPort)
+      || !m_statusServer.listen (QHostAddress::Any, m_statusPort))
+    {
+      emit errorOccurred (QStringLiteral ("Failed to listen: %1 / %2 / %3")
+                              .arg (m_commandServer.errorString ())
+                              .arg (m_imagingServer.errorString ())
+                              .arg (m_statusServer.errorString ()));
+      m_commandServer.close ();
+      m_imagingServer.close ();
+      m_statusServer.close ();
+      return;
+    }
+  m_listening = true;
+  emit listeningChanged ();
+  emit statusMessage (QStringLiteral ("Listening on ports %1/%2/%3…")
+                          .arg (m_commandPort)
+                          .arg (m_imagingPort)
+                          .arg (m_statusPort));
 }
 
 void
-Xpl2Client::disconnectFromServer ()
+Xpl2Client::stopListening ()
+{
+  m_commandServer.close ();
+  m_imagingServer.close ();
+  m_statusServer.close ();
+
+  auto cleanup = [] (QTcpSocket *&sock)
+    {
+      if (sock)
+        {
+          sock->disconnectFromHost ();
+          sock->deleteLater ();
+          sock = nullptr;
+        }
+    };
+  cleanup (m_commandSocket);
+  cleanup (m_imagingSocket);
+  cleanup (m_statusSocket);
+
+  if (m_listening)
+    {
+      m_listening = false;
+      emit listeningChanged ();
+    }
+  updateConnectedState ();
+}
+
+QTcpSocket *&
+Xpl2Client::socketForServer (QTcpServer *server)
 {
-  m_commandSocket.disconnectFromHost ();
-  m_imagingSocket.disconnectFromHost ();
-  m_statusSocket.disconnectFromHost ();
+  if (server == &m_commandServer)
+    return m_commandSocket;
+  if (server == &m_imagingServer)
+    return m_imagingSocket;
+  return m_statusSocket;
 }
 
 void
@@ -609,22 +646,22 @@ Xpl2Client::imageCount ()
 /* ------------------------------------------------------------------ */
 
 void
-Xpl2Client::sendCommand (QTcpSocket &socket, const QByteArray &command,
+Xpl2Client::sendCommand (QTcpSocket *socket, const QByteArray &command,
                          const QVariantList &params)
 {
-  if (socket.state () != QAbstractSocket::ConnectedState)
+  if (!socket || socket->state () != QAbstractSocket::ConnectedState)
     {
       emit errorOccurred (QStringLiteral ("Not connected for %1")
                               .arg (QString::fromUtf8 (command)));
       return;
     }
   QByteArray data = Xpl2Protocol::buildMessage (command, params);
-  socket.write (data);
+  socket->write (data);
 
   QByteArray wire;
   if (s_wireDebug)
     wire = " >> " + data.trimmed ();
-  qDebug ("%s TX %s%s", qPrintable (logTag (&socket)), command.constData (),
+  qDebug ("%s TX %s%s", qPrintable (logTag (socket)), command.constData (),
           wire.constData ());
 }
 
@@ -639,8 +676,8 @@ Xpl2Client::dispatchCommandMessage (const Xpl2Protocol::ParsedMessage &msg)
     handleGsJcVersion (msg.params);
   else if (msg.command == "GS_PH_VERSION")
     handleGsPhVersion (msg.params);
-  else if (!dispatchResponse (msg.command, msg.params, &m_commandSocket))
-    qWarning ("%s Unknown command: %s", qPrintable (logTag (&m_commandSocket)),
+  else if (!dispatchResponse (msg.command, msg.params, m_commandSocket))
+    qWarning ("%s Unknown command: %s", qPrintable (logTag (m_commandSocket)),
               msg.command.constData ());
 }
 
@@ -656,7 +693,7 @@ Xpl2Client::dispatchImagingMessage (const Xpl2Protocol::ParsedMessage &msg)
       int lines = 0;
       if (!msg.params.isEmpty ())
         lines = msg.params[0].toString ().toInt (nullptr, 16);
-      qDebug ("%s    n imageLines=%d", qPrintable (logTag (&m_imagingSocket)),
+      qDebug ("%s    n imageLines=%d", qPrintable (logTag (m_imagingSocket)),
               lines);
       emit statusMessage (QStringLiteral ("RX n: imageLines=%1").arg (lines));
       emit imagingReply (lines);
@@ -664,13 +701,13 @@ Xpl2Client::dispatchImagingMessage (const Xpl2Protocol::ParsedMessage &msg)
   else if (msg.command == "m4")
     {
       bool ok = !msg.params.isEmpty () && msg.params[0].toInt () == 1;
-      qDebug ("%s    m4 success=%d", qPrintable (logTag (&m_imagingSocket)),
+      qDebug ("%s    m4 success=%d", qPrintable (logTag (m_imagingSocket)),
               ok);
       emit statusMessage (QStringLiteral ("RX m4: success=%1").arg (ok));
       emit imagingStopResult (ok);
     }
-  else if (!dispatchResponse (msg.command, msg.params, &m_imagingSocket))
-    qWarning ("%s Unknown command: %s", qPrintable (logTag (&m_imagingSocket)),
+  else if (!dispatchResponse (msg.command, msg.params, m_imagingSocket))
+    qWarning ("%s Unknown command: %s", qPrintable (logTag (m_imagingSocket)),
               msg.command.constData ());
 }
 
@@ -685,13 +722,13 @@ Xpl2Client::dispatchStatusMessage (const Xpl2Protocol::ParsedMessage &msg)
     handleEvStatusMsgJc (msg.params);
   else if (msg.command == "EV_STATUS_MSG_PH")
     handleEvStatusMsgPh (msg.params);
-  else if (!dispatchResponse (msg.command, msg.params, &m_statusSocket))
-    qWarning ("%s Unknown command: %s", qPrintable (logTag (&m_statusSocket)),
+  else if (!dispatchResponse (msg.command, msg.params, m_statusSocket))
+    qWarning ("%s Unknown command: %s", qPrintable (logTag (m_statusSocket)),
               msg.command.constData ());
 }
 
 void
-Xpl2Client::handleKaPing (QTcpSocket &socket)
+Xpl2Client::handleKaPing (QTcpSocket *socket)
 {
   sendCommand (socket, "KA_PING", { 1 });
 }
@@ -709,7 +746,7 @@ Xpl2Client::handleGsJcVersion (const QVariantList &params)
   m_hardwareVersion = params[2].toString ();
   m_printheadCount = params[3].toInt ();
   qDebug ("%s    controller=%d fw=%s hw=%s phCount=%d",
-          qPrintable (logTag (&m_commandSocket)), m_controllerId,
+          qPrintable (logTag (m_commandSocket)), m_controllerId,
           qPrintable (m_firmwareVersion), qPrintable (m_hardwareVersion),
           m_printheadCount);
   emit statusMessage (
@@ -739,7 +776,7 @@ Xpl2Client::handleGsPhVersion (const QVariantList &params)
   QString bootVer = params[7].toString ();
   qDebug ("%s    PH[%d] mcuFw=%s mcuHw=%s mcuFwVar=%s fpgaFw=%s fpgaHw=%s "
           "boot=%s",
-          qPrintable (logTag (&m_commandSocket)), phId, qPrintable (mcuFw),
+          qPrintable (logTag (m_commandSocket)), phId, qPrintable (mcuFw),
           qPrintable (mcuHw), qPrintable (mcuFwVar), qPrintable (fpgaFw),
           qPrintable (fpgaHw), qPrintable (bootVer));
   emit statusMessage (
@@ -905,7 +942,7 @@ Xpl2Client::handleEvStatusMsgJc (const QVariantList &params)
 {
   Xpl2JcStatus status = Xpl2JcStatus::fromParams (params);
   qDebug ("%s    EV_STATUS_MSG_JC controller=%d level=%d temp=%.1f cpu=%.1f%%",
-          qPrintable (logTag (&m_statusSocket)), status.controllerId,
+          qPrintable (logTag (m_statusSocket)), status.controllerId,
           status.statusLevel, status.temperature, status.cpuPercentageBusy);
   emit statusMessage (
       QStringLiteral ("RX EV_STATUS_MSG_JC: controller=%1 level=%2")
@@ -919,7 +956,7 @@ Xpl2Client::handleEvStatusMsgPh (const QVariantList &params)
 {
   Xpl2PhStatus status = Xpl2PhStatus::fromParams (params);
   qDebug ("%s    EV_STATUS_MSG_PH controller=%d level=%d ph=%d temp=%.1f",
-          qPrintable (logTag (&m_statusSocket)), status.controllerId,
+          qPrintable (logTag (m_statusSocket)), status.controllerId,
           status.statusLevel, status.printheadId, status.temperature);
   emit statusMessage (
       QStringLiteral ("RX EV_STATUS_MSG_PH: controller=%1 level=%2 ph=%3")
@@ -937,9 +974,12 @@ void
 Xpl2Client::updateConnectedState ()
 {
   bool allConnected
-      = m_commandSocket.state () == QAbstractSocket::ConnectedState
-        && m_imagingSocket.state () == QAbstractSocket::ConnectedState
-        && m_statusSocket.state () == QAbstractSocket::ConnectedState;
+      = m_commandSocket
+        && m_commandSocket->state () == QAbstractSocket::ConnectedState
+        && m_imagingSocket
+        && m_imagingSocket->state () == QAbstractSocket::ConnectedState
+        && m_statusSocket
+        && m_statusSocket->state () == QAbstractSocket::ConnectedState;
   if (m_connected == allConnected)
     return;
   m_connected = allConnected;
@@ -951,17 +991,17 @@ Xpl2Client::logTag (const QTcpSocket *socket) const
 {
   const char *name = "Unknown";
   quint16 port = 0;
-  if (socket == &m_commandSocket)
+  if (socket == m_commandSocket)
     {
       name = "Command";
       port = m_commandPort;
     }
-  else if (socket == &m_imagingSocket)
+  else if (socket == m_imagingSocket)
     {
       name = "Imaging";
       port = m_imagingPort;
     }
-  else if (socket == &m_statusSocket)
+  else if (socket == m_statusSocket)
     {
       name = "Status";
       port = m_statusPort;
@@ -975,26 +1015,46 @@ Xpl2Client::logTag (const QTcpSocket *socket) const
 /* ------------------------------------------------------------------ */
 
 void
-Xpl2Client::onSocketConnected ()
+Xpl2Client::onNewConnection ()
 {
-  auto *socket = qobject_cast<QTcpSocket *> (sender ());
-  qInfo ("%s Connected", qPrintable (logTag (socket)));
-  updateConnectedState ();
+  auto *server = qobject_cast<QTcpServer *> (sender ());
+  QTcpSocket *&slot = socketForServer (server);
+
+  while (auto *pending = server->nextPendingConnection ())
+    {
+      if (slot)
+        {
+          qWarning ("%s Rejected extra connection",
+                    qPrintable (logTag (slot)));
+          pending->deleteLater ();
+          continue;
+        }
+      slot = pending;
+      connect (slot, &QTcpSocket::readyRead, this,
+               &Xpl2Client::onSocketMessageReady);
+      connect (slot, &QTcpSocket::disconnected, this,
+               &Xpl2Client::onSocketDisconnected);
+      connect (slot, &QAbstractSocket::errorOccurred, this,
+               &Xpl2Client::onSocketError);
+      qInfo ("%s Controller connected", qPrintable (logTag (slot)));
+      updateConnectedState ();
+    }
 }
 
 void
 Xpl2Client::onSocketDisconnected ()
 {
   auto *socket = qobject_cast<QTcpSocket *> (sender ());
-  if (!socket)
-    {
-      /* Identify by elimination — which socket just left ConnectedState? */
-      for (auto *s : { &m_commandSocket, &m_imagingSocket, &m_statusSocket })
-        if (s->state () != QAbstractSocket::ConnectedState)
-          qInfo ("%s Disconnected", qPrintable (logTag (s)));
-    }
-  else
-    qInfo ("%s Disconnected", qPrintable (logTag (socket)));
+  qInfo ("%s Controller disconnected", qPrintable (logTag (socket)));
+
+  if (socket == m_commandSocket)
+    m_commandSocket = nullptr;
+  else if (socket == m_imagingSocket)
+    m_imagingSocket = nullptr;
+  else if (socket == m_statusSocket)
+    m_statusSocket = nullptr;
+
+  socket->deleteLater ();
   updateConnectedState ();
 }
 
@@ -1014,9 +1074,9 @@ Xpl2Client::onSocketMessageReady ()
           qDebug ("%s RX %s%s", qPrintable (logTag (socket)),
                   msg.command.constData (), wire.constData ());
 
-          if (socket == &m_commandSocket)
+          if (socket == m_commandSocket)
             dispatchCommandMessage (msg);
-          else if (socket == &m_imagingSocket)
+          else if (socket == m_imagingSocket)
             dispatchImagingMessage (msg);
           else
             dispatchStatusMessage (msg);