Hi,
I've a problem with using the QTcpSocket.
I ty to write a programm to interact with a database over tcp.
I have to use this way because the database is not normaly supported by Qt (it's TinySQL database).

Here are my code so far:
Qt Code: 
  1. void connectToServer(void){
  2. pushButton_abfragen->setText(tr("Abfragen 2......"));
  3. tcpsocket.connectToHost(lineEdit_ipgypsy->text(),5050);
  4. pushButton_abfragen->setText(tr("Abfragen ......"));
  5. pushButton_upload->setEnabled(false);
  6. pushButton_abfragen->setEnabled(false);    		
  7.  
  8. };//connectToServer
  9.  
  10. void  sendRequest(void){
  11.  
  12. QByteArray block;
  13. QDataStream out(&block, QIODevice::WriteOnly);
  14. out.setVersion(QDataStream::Qt_4_2);
  15. QString abfrage("SELECT * FROM Datum; \r\n");
  16.  
  17.  
  18. out  << abfrage.toAscii();
  19. out.device()->seek(0);
  20. out << quint16(block.size() - sizeof(quint16));
  21. tcpsocket.write(block);
  22. pushButton_abfragen->setText(tcpsocket.errorString());
  23.  
  24. };//sendRequest 
  25.  
  26. void  getData(void){
  27. 	pushButton_abfragen->setText(tr("Abfragen 2......"));
  28. 	//pushButton_abfragen->setText(tcpsocket.errorString()+"   --1");
  29.  
  30.    	QFile confdatei("testdata.txt");
  31.    	confdatei.open(QIODevice::WriteOnly);
  32.    	QDataStream conf(&confdatei);
  33.  	QByteArray ip,wert,datum;
  34.     conf.setVersion(QDataStream::Qt_4_2);
  35.  
  36. 	//pushButton_abfragen->setText(tcpsocket.errorString()+"   --2");    
  37.  
  38.      QDataStream in(&tcpsocket);
  39.      in.setVersion(QDataStream::Qt_4_2);
  40.  
  41.  	//pushButton_abfragen->setText(tcpsocket.errorString()+"   --3");
  42.  
  43.      forever{
  44.  
  45.      if(nextBlockSize == 0){
  46.      if(tcpsocket.bytesAvailable() < sizeof(quint16)){ break; }
  47.      	in >> nextBlockSize;	
  48.      }	
  49.      if(nextBlockSize == 0xFFFF){
  50.      	closeConnection();
  51.    		break;  	
  52.      }
  53.      if(tcpsocket.bytesAvailable() < nextBlockSize){ break;}
  54.  
  55.     conf << in;//ip << wert << datum; 
  56.  
  57.  
  58.      	nextBlockSize = 0;
  59.      }
  60.  
  61.  
  62.  
  63.  
  64.  
  65. };//getData
  66.  
  67. void  closeConnection(void){
  68.  
  69. tcpsocket.close();
  70. pushButton_abfragen->setText(tr("Daten abfragen"));
  71. pushButton_upload->setEnabled(true);
  72. pushButton_abfragen->setEnabled(true);   
  73.  
  74. };//closeConnection
  75.  
  76. void displayError(QAbstractSocket::SocketError socketError)
  77.  {
  78.      switch (socketError) {
  79.      case QAbstractSocket::RemoteHostClosedError:
  80.          break;
  81.      case QAbstractSocket::HostNotFoundError:
  82.          QMessageBox::information(this, tr("Fortune Client"),
  83.                                   tr("The host was not found. Please check the "
  84.                                      "host name and port settings."));
  85.          pushButton_abfragen->setText(tr("Daten abfragen"));
  86. 		 pushButton_upload->setEnabled(true);
  87. 		 pushButton_abfragen->setEnabled(true);
  88.          break;
  89.      case QAbstractSocket::ConnectionRefusedError:
  90.          QMessageBox::information(this, tr("Fortune Client"),
  91.                                   tr("The connection was refused by the peer. "
  92.                                      "Make sure the fortune server is running, "
  93.                                      "and check that the host name and port "
  94.                                      "settings are correct."));
  95.          pushButton_abfragen->setText(tr("Daten abfragen"));
  96.          pushButton_upload->setEnabled(true);
  97.          pushButton_abfragen->setEnabled(true);
  98.          break;
  99.      default:
  100.          QMessageBox::information(this, tr("Fortune Client"),
  101.                                   tr("The following error occurred: %1.")
  102.                                   .arg(tcpsocket.errorString()));
  103.          pushButton_abfragen->setText(tr("Daten abfragen"));
  104. 		 pushButton_upload->setEnabled(true);
  105. 		 pushButton_abfragen->setEnabled(true);
  106.      }
  107.  
  108.  
  109.  }
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tcpsocket and nextBlockSize are member variables. And all connect - calls are made.
I think the problem is the line:
Qt Code: 
  1. QString abfrage("SELECT * FROM Datum; \r\n");
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If I send this line the readyRead() signal is emitted, and then direkt the disconnected() signal in response. I never get a error by the displayError slot.
I thought the prolem is \r\n and I try to use \0 and single \n and so on.
But it is all the same.
So what's wrong? At the moment I have no idea what I can try out.
Greetings,
SuperSonik