I have two programs, A and B, who communicate by an UDP connection. They can beings on the same computer or two computers on a network.
The A program sends a command to the B program, which processes this command and sends then an answer to the A program.
Originally both programs were written in C# (WinXP). The A program was rewritten with Qt/C++, and it works well with the C# version of B (WinXP).
But I don't manage to put on the UDP connection with a Qt/C++ version of B.
Part of the A program
Qt Code: 
  1. class radioInterfaceThread : public QThread
  2. {
  3. 	Q_OBJECT
  4.  
  5. 	QUdpSocket	*udpCommandSocket;
  6.  
  7. public:
  8. 	radioInterfaceThread(QObject *parent = 0);
  9. 	~radioInterfaceThread();
  10. 	void setConnectUDP();
  11. protected:
  12. 	void run();
  13. private slots:
  14. 	void udpRxEvent();
  15. 	void sendCommand();
  16. };
  17.  
  18.  
  19. radioInterfaceThread::radioInterfaceThread(QObject *parent)
  20. 	: QThread(parent)
  21.     , udpCommandSocket(0)
  22. {
  23. 	udpCommandSocket = new QUdpSocket;
  24. 	connect(udpCommandSocket, SIGNAL(readyRead()), this, SLOT(udpRxEvent()), Qt::DirectConnection);
  25. }
  26.  
  27. void radioInterfaceThread::run()
  28. {
  29. 	....
  30. 	exec();
  31. 	....
  32. }
  33.  
  34.  
  35. void radioInterfaceThread::setConnectTCP(QString addr, quint16 port)
  36. {
  37. 	udpCommandSocket->connectToHost(QHostAddress(addr), port, QAbstractSocket::ReadWrite);
  38. }
  39.  
  40.  
  41. void radioInterfaceThread::udpRxEvent()
  42. {
  43. 	qint64 bytes_available = 0;
  44.  
  45. 	while ((bytes_available = udpCommandSocket->bytesAvailable()) > 0)
  46. 	{
  47. 		QByteArray datagram;
  48. 		datagram.resize(bytes_available);
  49.  
  50. 		qint64 bytes_read = udpCommandSocket->readDatagram(datagram.data(), datagram.size());
  51. 		//... process the answer
  52. 	}
  53. }
  54.  
  55. // slot called to send Command
  56. void radioInterfaceThread::sendCommand(QString cmd)
  57. {
  58. 	qint64 bytes_sent = 0;
  59.  
  60. 	//...
  61. 	bytes_sent = udpCommandSocket->write(QString(cmd.trimmed() + "\r\n").toLatin1().constData());
  62. 	//...
  63. }
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