Fixing Qt event loop issue where UDP readReady signal would stop working.

src/comm/UDPLink.cc

@@ -80,6 +80,7 @@ UDPLink::UDPLink(UDPConfiguration* config)
     #if defined(QGC_ZEROCONF_ENABLED)
     , _dnssServiceRef(NULL)
     #endif
+    , _running(false)
 {
     Q_ASSERT(config != NULL);
     _config = config;
@@ -98,9 +99,12 @@ UDPLink::~UDPLink()
     _config->setLink(NULL);
     _disconnect();
     // Tell the thread to exit
-    quit();
+    _running = false;
     // Wait for it to exit
     wait();
+    while(_outQueue.count() > 0) {
+        delete _outQueue.dequeue();
+    }
     this->deleteLater();
 }
 
@@ -110,8 +114,16 @@ UDPLink::~UDPLink()
  **/
 void UDPLink::run()
 {
-    _hardwareConnect();
-    exec();
+    if(_hardwareConnect()) {
+        while(true) {
+            readBytes();
+            if(_writeBytes() && _running)
+                continue;
+            if(!_running)
+                break;
+            this->msleep(50);
+        }
+    }
     if (_socket) {
         _deregisterZeroconf();
         _socket->close();
@@ -149,39 +161,42 @@ void UDPLink::writeBytes(const char* data, qint64 size)
     if (!_socket) {
         return;
     }
-
-    // Broadcast to all connected systems
-    QString host;
-    int port;
-    if(_config->firstHost(host, port)) {
-        do {
-            if(UDPLINK_DEBUG) {
-                QString bytes;
-                QString ascii;
-                for (int i=0; i<size; i++)
-                {
-                    unsigned char v = data[i];
-                    bytes.append(QString().sprintf("%02x ", v));
-                    if (data[i] > 31 && data[i] < 127)
-                    {
-                        ascii.append(data[i]);
-                    }
-                    else
-                    {
-                        ascii.append(219);
-                    }
+    QByteArray* qdata = new QByteArray(data, size);
+    QMutexLocker lock(&_mutex);
+    _outQueue.enqueue(qdata);
+}
+
+
+bool UDPLink::_writeBytes()
+{
+    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);
                 }
-                qDebug() << "Sent" << size << "bytes to" << host << ":" << port << "data:";
-                qDebug() << bytes;
-                qDebug() << "ASCII:" << ascii;
+                // 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(host);
             }
-            QHostAddress currentHost(host);
-            _socket->writeDatagram(data, size, currentHost, (quint16)port);
-            // 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));
+        }
+        delete qdata;
+        lock.relock();
     }
+    return (_outQueue.count() > 0);
 }
 
 /**
@@ -220,6 +235,8 @@ 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)
+            break;
     }
 }
 
@@ -230,8 +247,8 @@ void UDPLink::readBytes()
  **/
 bool UDPLink::_disconnect(void)
 {
-    this->quit();
-    this->wait();
+    _running = false;
+    wait();
     if (_socket) {
         // Make sure delete happen on correct thread
         _socket->deleteLater();
@@ -252,12 +269,13 @@ bool UDPLink::_connect(void)
 {
     if(this->isRunning())
     {
-        this->quit();
-        this->wait();
+        _running = false;
+        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;
 }
@@ -268,13 +286,12 @@ bool UDPLink::_hardwareConnect()
         delete _socket;
         _socket = NULL;
     }
-    QHostAddress host = QHostAddress::Any;
+    QHostAddress host = QHostAddress::AnyIPv4;
     _socket = new QUdpSocket();
     _socket->setProxy(QNetworkProxy::NoProxy);
     _connectState = _socket->bind(host, _config->localPort(), QAbstractSocket::ReuseAddressHint);
     if (_connectState) {
         _registerZeroconf(_config->localPort(), kZeroconfRegistration);
-        QObject::connect(_socket, SIGNAL(readyRead()), this, SLOT(readBytes()));
         emit connected();
     } else {
         emit communicationError("UDP Link Error", "Error binding UDP port");
@@ -408,7 +425,7 @@ void UDPConfiguration::addHost(const QString& host, int port)
             qWarning() << "UDP:" << "Could not resolve host:" << host << "port:" << port;
         } else {
             _hosts[ipAdd] = port;
-            //qDebug() << "UDP:" << "Adding Host:" << ipAdd << ":" << port;
+            qDebug() << "UDP:" << "Adding Host:" << ipAdd << ":" << port;
         }
     }
 }
@@ -423,7 +440,10 @@ void UDPConfiguration::removeHost(const QString& host)
     tHost = tHost.trimmed();
     QMap<QString, int>::iterator i = _hosts.find(tHost);
     if(i != _hosts.end()) {
+        qDebug() << "UDP:" << "Removed host:" << host;
         _hosts.erase(i);
+    } else {
+        qWarning() << "UDP:" << "Could not remove unknown host:" << host;
     }
 }
 

src/comm/UDPLink.h

@@ -36,6 +36,9 @@ This file is part of the QGROUNDCONTROL project
 #include <QMap>
 #include <QMutex>
 #include <QUdpSocket>
+#include <QMutexLocker>
+#include <QQueue>
+#include <QByteArray>
 
 #if defined(QGC_ZEROCONF_ENABLED)
 #include <dns_sd.h>
@@ -212,8 +215,11 @@ private:
     DNSServiceRef  _dnssServiceRef;
 #endif
 
-signals:
-    //Signals are defined by LinkInterface
+    bool                _running;
+    QMutex              _mutex;
+    QQueue<QByteArray*> _outQueue;
+
+    bool _writeBytes    ();
 
 };