Make the fix dependent on the Qt version.

src/comm/UDPLink.cc

@@ -28,6 +28,13 @@ This file is part of the QGROUNDCONTROL project
  *
  */
 
+#include <QtGlobal>
+#if QT_VERSION > 0x050401
+#define UDP_BROKEN_SIGNAL 1
+#else
+#define UDP_BROKEN_SIGNAL 0
+#endif
+
 #include <QTimer>
 #include <QList>
 #include <QDebug>
@@ -100,6 +107,7 @@ UDPLink::~UDPLink()
     _disconnect();
     // Tell the thread to exit
     _running = false;
+    quit();
     // Wait for it to exit
     wait();
     while(_outQueue.count() > 0) {
@@ -115,13 +123,24 @@ UDPLink::~UDPLink()
 void UDPLink::run()
 {
     if(_hardwareConnect()) {
-        while(true) {
-            readBytes();
-            if(_writeBytes() && _running)
-                continue;
-            if(!_running)
-                break;
-            this->msleep(50);
+        if(UDP_BROKEN_SIGNAL) {
+            bool loop = false;
+            while(true) {
+                //-- Anything to read?
+                loop = _socket->hasPendingDatagrams();
+                if(loop) {
+                    readBytes();
+                }
+                //-- Loop right away if busy
+                if((_dequeBytes() || loop) && _running)
+                    continue;
+                if(!_running)
+                    break;
+                //-- Settle down (it gets here if there is nothing to read or write)
+                this->msleep(50);
+            }
+        } else {
+            exec();
         }
     }
     if (_socket) {
@@ -154,51 +173,58 @@ void UDPLink::removeHost(const QString& host)
     _config->removeHost(host);
 }
 
-#define UDPLINK_DEBUG 0
-
 void UDPLink::writeBytes(const char* data, qint64 size)
 {
     if (!_socket) {
         return;
     }
-    QByteArray* qdata = new QByteArray(data, size);
-    QMutexLocker lock(&_mutex);
-    _outQueue.enqueue(qdata);
+    if(UDP_BROKEN_SIGNAL) {
+        QByteArray* qdata = new QByteArray(data, size);
+        QMutexLocker lock(&_mutex);
+        _outQueue.enqueue(qdata);
+    } else {
+        _sendBytes(data, size);
+    }
 }
 
 
-bool UDPLink::_writeBytes()
+bool UDPLink::_dequeBytes()
 {
     QMutexLocker lock(&_mutex);
     if(_outQueue.count() > 0) {
         QByteArray* qdata = _outQueue.dequeue();
         lock.unlock();
-        QStringList goneHosts;
-        // Send to all connected systems
-        QString host;
-        int port;
-        if(_config->firstHost(host, port)) {
-            do {
-                QHostAddress currentHost(host);
-                if(_socket->writeDatagram(qdata->data(), qdata->size(), currentHost, (quint16)port) < 0) {
-                    // This host is gone. Add to list to be removed
-                    goneHosts.append(host);
-                }
-                // Log the amount and time written out for future data rate calculations.
-                QMutexLocker dataRateLocker(&dataRateMutex);
-                logDataRateToBuffer(outDataWriteAmounts, outDataWriteTimes, &outDataIndex, qdata->size(), QDateTime::currentMSecsSinceEpoch());
-            } while (_config->nextHost(host, port));
-            //-- Remove hosts that are no longer there
-            foreach (QString ghost, goneHosts) {
-                _config->removeHost(ghost);
-            }
-        }
+        _sendBytes(qdata->data(), qdata->size());
         delete qdata;
         lock.relock();
     }
     return (_outQueue.count() > 0);
 }
 
+void UDPLink::_sendBytes(const char* data, qint64 size)
+{
+    QStringList goneHosts;
+    // Send to all connected systems
+    QString host;
+    int port;
+    if(_config->firstHost(host, port)) {
+        do {
+            QHostAddress currentHost(host);
+            if(_socket->writeDatagram(data, size, currentHost, (quint16)port) < 0) {
+                // This host is gone. Add to list to be removed
+                goneHosts.append(host);
+            }
+            // Log the amount and time written out for future data rate calculations.
+            QMutexLocker dataRateLocker(&dataRateMutex);
+            logDataRateToBuffer(outDataWriteAmounts, outDataWriteTimes, &outDataIndex, size, QDateTime::currentMSecsSinceEpoch());
+        } while (_config->nextHost(host, port));
+        //-- Remove hosts that are no longer there
+        foreach (QString ghost, goneHosts) {
+            _config->removeHost(ghost);
+        }
+    }
+}
+
 /**
  * @brief Read a number of bytes from the interface.
  **/
@@ -235,7 +261,7 @@ void UDPLink::readBytes()
         // would trigger this.
         // Add host to broadcast list if not yet present, or update its port
         _config->addHost(sender.toString(), (int)senderPort);
-        if(!_running)
+        if(UDP_BROKEN_SIGNAL && !_running)
             break;
     }
 }
@@ -248,6 +274,7 @@ void UDPLink::readBytes()
 bool UDPLink::_disconnect(void)
 {
     _running = false;
+    quit();
     wait();
     if (_socket) {
         // Make sure delete happen on correct thread
@@ -255,9 +282,8 @@ bool UDPLink::_disconnect(void)
         _socket = NULL;
         emit disconnected();
     }
-    // TODO When would this ever return false?
     _connectState = false;
-    return !_connectState;
+    return true;
 }
 
 /**
@@ -267,17 +293,15 @@ bool UDPLink::_disconnect(void)
  **/
 bool UDPLink::_connect(void)
 {
-    if(this->isRunning())
+    if(this->isRunning() || _running)
     {
         _running = false;
+        quit();
         wait();
     }
-    // TODO When would this ever return false?
-    bool connected = true;
-    // I see no reason to run this in "HighPriority"
     _running = true;
     start(NormalPriority);
-    return connected;
+    return true;
 }
 
 bool UDPLink::_hardwareConnect()
@@ -292,6 +316,10 @@ bool UDPLink::_hardwareConnect()
     _connectState = _socket->bind(host, _config->localPort(), QAbstractSocket::ReuseAddressHint);
     if (_connectState) {
         _registerZeroconf(_config->localPort(), kZeroconfRegistration);
+        //-- Connect signal if this version of Qt is not broken
+        if(!UDP_BROKEN_SIGNAL) {
+            QObject::connect(_socket, SIGNAL(readyRead()), this, SLOT(readBytes()));
+        }
         emit connected();
     } else {
         emit communicationError("UDP Link Error", "Error binding UDP port");

src/comm/UDPLink.h

@@ -219,7 +219,8 @@ private:
     QMutex              _mutex;
     QQueue<QByteArray*> _outQueue;
 
-    bool _writeBytes    ();
+    bool _dequeBytes    ();
+    void _sendBytes     (const char* data, qint64 size);
 
 };