TCP Socket not connecting on Release

[^NyAw^]

Hi,

Sorry, I'm developing Modbus protocol and I have some layers. The layer that I show you is the CModbusTCPMaster, and the socket is delivered to the CModbusTCPTransport:

I had simplified it because it's a bit large code.

void CModbusTCPTransport::setSocket(QTcpSocket* pqSocket)
{
    bool bC1 = connect(m_pqTCPSocket,SIGNAL(readyRead()),this,SLOT(readResponse()));
    bool bC2 = connect(m_pqTCPSocket,SIGNAL(disconnected()),this,SLOT(disconect()));
}

void CModbusTCPTransport::setSocket(QTcpSocket* pqSocket)
{
    bool bC1 = connect(m_pqTCPSocket,SIGNAL(readyRead()),this,SLOT(readResponse()));
    bool bC2 = connect(m_pqTCPSocket,SIGNAL(disconnected()),this,SLOT(disconect()));
}

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void CModbusTCPTransport::sendRequest(CModbusRequest* request)
{
    int iLength = 8;
    char* pcRequest = new char[260];
    pcRequest[0] = request->getTransaction() >> 8;
    pcRequest[1] = request->getTransaction();
    pcRequest[2] = request->getProtocol() >> 8;
    pcRequest[3] = request->getProtocol();
    pcRequest[4] = request->getLength() >> 8;
    pcRequest[5] = request->getLength();
    pcRequest[6] = request->getUnitID();
 
    pcRequest[7] = request->getFunctionCode();
 
    m_pqTCPSocket->write(pcRequest,iLength);
    //Force the Request to be sent
    m_pqTCPSocket->flush();
    delete[] pcRequest;
}
 
void CModbusTCPTransport::readResponse()
{
    //Read the Modbus Header (8 bytes)
    qint64 bytesRead = m_pqTCPSocket->read(m_cbuffer,8);
}

void CModbusTCPTransport::sendRequest(CModbusRequest* request)
{
    int iLength = 8;
    char* pcRequest = new char[260];
    pcRequest[0] = request->getTransaction() >> 8;
    pcRequest[1] = request->getTransaction();
    pcRequest[2] = request->getProtocol() >> 8;
    pcRequest[3] = request->getProtocol();
    pcRequest[4] = request->getLength() >> 8;
    pcRequest[5] = request->getLength();
    pcRequest[6] = request->getUnitID();

    pcRequest[7] = request->getFunctionCode();

    m_pqTCPSocket->write(pcRequest,iLength);
    //Force the Request to be sent
    m_pqTCPSocket->flush();
    delete[] pcRequest;
}

void CModbusTCPTransport::readResponse()
{
    //Read the Modbus Header (8 bytes)
    qint64 bytesRead = m_pqTCPSocket->read(m_cbuffer,8);
}

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Thanks,

[^NyAw^]

Hi,

Creating a QObject inside "run()" method of the Thread, shows this error:

void myThread::run()
{
  ...
  QObject ob(this);
}

void myThread::run()
{
  ...
  QObject ob(this);
}

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QObject: Cannot create children for a parent that is in a different thread.
(Parent is CModbusTCPMaster(02BCAAB0), parent's thread is QThread(019480E0), current thread is CModbusTCPMaster(02BCAAB0)

I tryied this because when creating the socket, no parent is passed to it. But trying to use "this" as the socket parents gets me the same error.

Thanks,

[^NyAw^]

Hi,

I have an idea how to solve this:
-Create a QTcpSocket dervied class that has a SLOT "sendMessage(char*)"
-My Thread emits a SIGNAL "readySend(char*)" that is connected to the SLOT of the QTcpSocket derived class on a QueuedConnection.

The problem is that when calling "pqTcpSocket->write", this is done by myThread.

Thanks,

[^NyAw^]

Hi,

The QSocketNotifier messages have disapeared using this behaviour.

The other problem that the server application is not accepting the connection is still getting me errors, but using a simple Qt server aplication it connects well. So, I really don't understand why the other server application is reaching the connection with "QAbstractSocket::RemoteHostClosedError" error code(note that is a third party app that I don't have the source code).

And finally, the problem that the server recives a different message ... is still getting me a different message.

Thanks,

[wysota]

But trying to use "this" as the socket parents gets me the same error

Because the child and parent objects are created in different threads and this is forbidden. Don't try to pass a parent.

And finally, the problem that the server recives a different message ... is still getting me a different message.

Are the sender and receiver machines of the same architecture (32/64b big/little endianness)?

Could you check using a network sniffer whether the content "turns incorrect" on the client or on the server? In other words - what is being transmitted over the network? The data that is being sent or the one that is being received?

[^NyAw^]

Hi,

I'm using the same machine to use client and server apps. A Windows XP OS on a 32 bit machine and Qt 4.3.0.

Wireshark sniffer is not able to capture packages from/to the same machine, so I open a QFile and write the message(increasing by 48 to convert int to char ona ASCII) into it.

The data that the client is sending is wrong when using Release but it's okay when running on Debug.

Thanks,

[Bitto]

Ã’scar, I'm sure everybody would like to help, but if you want an accurate answer, you will have to isolate your problem, and post a standalone compilable example that shows the bug.

Usually differences in behavior between debug and release in networking code are caused by either

1) Timing problems (i.e., race conditions)
* the order of packet arrival affects you program's logics

2) Network packet fragmentation (i.e., partial packet arrival)
* the size of packets received affects your program's behavior

3) Compiler bugs
* _usually_ triggered by complex code, try simplifying

Generally though I'd try to simplify and simplify your code until you have something that's still broken, but can be posted to this forum for review :-).

[^NyAw^]

Hi,

1) Timing problems (i.e., race conditions)
* the order of packet arrival affects you program's logics

Really do you thing that I do different things on Debug and on Release?

2) Network packet fragmentation (i.e., partial packet arrival)
* the size of packets received affects your program's behavior

The packet size is as maximum 20 bytes long. Dou you really thing that it is packed on different little packages? But, when Debugging the packages that I recive are ok.

3) Compiler bugs
* _usually_ triggered by complex code, try simplifying

Simply I can't.

Will try to reproduce the problem.