Question

我正在实现基于Qt的TCP-Ip服务器的客户端，但是当我关闭连接时程序崩溃并通过点击连接按钮再次启动。

项目概述。我有两个lineEdit的Qwidget（主应用程序）供用户输入端口号和服务器IP地址。它还有2个连接到服务器和断开连接的按钮。在点击连接按钮时，它将调用客户端套接字的构造函数并调用connectToHost。

测试：尝试在同一台计算机上进行测试，服务器在端口6000上运行，ip地址为127.0.0.1。

问题：当我启动客户端应用程序时。输入端口号和地址并按下连接按钮，它成功连接。我可以成功写入服务器。然后我点击断开连接按钮并成功断开连接，但之后如果我再次通过点击连接按钮连接它会崩溃。我知道问题在于tcpSocket，但不知道如何修复它。

clientAgent（QWidget appilciation）.h

namespace Ui {
class ClientAgent;
}

class ClientAgent : public QWidget
{
    Q_OBJECT

public:
    explicit ClientAgent(QWidget *parent = 0);
    ~ClientAgent();

private:
    Ui::ClientAgent  *ui;
    ClientForTest    *tcpSockForTest;

// Qwidget declartion
below
....

private slots:
    void startClient();
    void stopClient();

public slots:
    void getCliReqTextChanged();

};

ClientAgent.cpp

ClientAgent::ClientAgent( QWidget *parent ) :
          QWidget(parent),
          ui( new Ui::ClientAgent )
{

// Widget declartion and initilisation
// Layout design etc

   //define signals and slots for Client
  // signals and slots

  connect( btnStartClient,  SIGNAL( clicked() ), this, SLOT( startClient() ) );
  connect( btnStopClient,   SIGNAL( clicked() ), this, SLOT( stopClient() ) );

// for write
connect( lEditCliReq,  SIGNAL( textChanged(const QString& ) ), this, SLOT( getCliReqTextChanged() ) );

  ui->setupUi( this );

}

ClientAgent::~ClientAgent()
{
    delete ui;
}


void ClientAgent::startClient()
{
  qDebug() << " we are in strt Clinet";
  qDebug() << " connecting ";

  // get server address and port number from GUI

  QString testAddr = lEditAddr->text();
  QString testPort = lEditPrt->text();

  tcpSockForTest = new ClientForTest( testAddr, testPort.toInt(), this );

  if( tcpSockForTest->connectToServer() == true )
   {
      lblCliStatus->setText(" connected ....");
   }
  else
   {
      lblCliStatus->setText(" failed to connect....");
   }

}

void ClientAgent::stopClient()
{
  qDebug() << " disconnecting ";
  tcpSockForTest->disconnectToServer();
  delete tcpSockForTest;
}

ClientForTest.h

class ClientForTest : public QObject
{
  Q_OBJECT
public:
  ClientForTest( QString hostAddr, quint16 portNum, QObject *parent );

  bool connectToServer();
  void disconnectToServer();
  QString getStoreMsgFrmCliReq( ) const;

  void writeToTest(const QString& stripCmd );
  void executeSignals();

    ~ClientForTest();

signals:
  void sigSendData();

public slots:
  void connectedToTest();
  void connectionClosedByServer();
  void error();

private:
   QTcpSocket   *sockFortest;
   QString       hostName;
   quint16       portNumber;
   quint16       nextBlockSize;
   QString       storeLineEditMsg;// store message from lineEditCliReq;

  };

ClientForTest.cpp

ClientForTest::ClientForTest( QString hostAddr, quint16 portNum, QObject *parent ) :
                            hostName( hostAddr ),
                            portNumber( portNum ),
                            QObject( parent )
{
  connect( sockFortest, SIGNAL( connected() ), this, SLOT( connectedToTest() ) );
  connect( sockFortest, SIGNAL( disconnected() ), this, SLOT( connectionClosedByServer() ) );
  connect( sockFortest, SIGNAL( error( QAbstractSocket::SocketError ) ), this, SLOT( error() ) );

  storeLineEditMsg = "";
}
void ClientForTest::executeSignals()
{
// actually I need toplace itin constructor will do later on
 connect( this,  SIGNAL( sigSendData() ), this, SLOT( connectedToTest() ) );
}

ClientForTest::~ClientForTest()
{

  sockFortest->close();
  delete sockFortest;
}

bool ClientForTest::connectToServer()
{
  sockFortest = new QTcpSocket( this->parent() ); // COULD be Probelm here but how to fix it?
  sockFortest->connectToHost( hostName, portNumber );
  nextBlockSize = 0;
  executeSignals();
  return sockFortest->waitForConnected(1000);
}

void ClientForTest::disconnectToServer()
{
  sockFortest->close();
  //sockFortest.close();
  qDebug() << "in disconnect for Test ";
  emit updateLabelinParent( updateStatusDis );
}


void ClientForTest::connectionClosedByServer()
{

  qDebug() << "connection closed by server ";
  if( nextBlockSize != 0xFFFF )
  {
    disconnectToServer();
  }
}

void ClientForTest::error()
{
  qDebug() << "in error ";
  disconnectToServer();
}

void ClientForTest::writeToTest( const QString& stripCmd )
{
  storeLineEditMsg = stripCmd;
  if( sockFortest->state() == QTcpSocket::UnconnectedState )
  {
      sockFortest->close();
      delete sockFortest; 
      sockFortest = new QTcpSocket( this->parent() );
      if( connectToServer() == true )
      {
         qDebug() << " YEEEE CONNECTED AGAIN finally ";
      }
  }
  if( sockFortest->state() == QTcpSocket::ConnectedState )
   {
      qDebug() << " YEEEE CONNECTED";
      sigSendData();
   }
}


void ClientForTest::connectedToTest( )
{
  QByteArray block;
  QDataStream out( &block, QIODevice::WriteOnly );

  out.setVersion( QDataStream::Qt_4_3 );

  QString stripCmd = getStoreMsgFrmCliReq(); // received info for some other function I havnt shown that func here

   out << quint16( 0 ) << stripCmd;

  out.device()->seek( 0 );

  out << quint16( block.size() - sizeof( quint16 ) );

  qDebug()<<" yeeeee connected state...";

  sockFortest->write( block );

  //reset storeLineEditMessage
  storeLineEditMsg.clear();
}

Answer 1

有些事情可能会导致您的崩溃：

您连接ClientForTest构造函数中的信号，但稍后会创建套接字本身。那不会奏效。在连接

sockFortest = new QTcpSocket(this);

同一行，请使用this代替this->parent()
最后：您创建/删除套接字有多个位置。不要这样做。在this为父级的构造函数内创建套接字，即可。在connectToServer中，建立连接，然后在disconnectToServer中使用disconnectFromHost关闭它。 startClient和stopClient也是如此。创建一次对象，只使用连接/断开功能，不删除。

如果需要代码，我可以添加一些。

自从被要求以来，这里有更多解释：

当然您可以使用父级，但在您的情况下，ClientForTest也是QObject。如果将ClientForTest设置为套接字的父级，将小组件设置为ClientForTest的父级，则它们将被正确清理。如果您使用this->parent()，则两者都将被销毁＆＃34;同时＃34;。但是，首先是Qt更改顺序，因此您的套接字可能会在ClientForTest之前销毁。 ClientForTest的析构函数会崩溃。如果套接字是ClientForTest
close()和disconnectFromHost()之间的主要区别在于第一个实际上关闭了OS套接字，而第二个实际上没有。问题是，在套接字关闭后，您无法使用它来创建新连接。因此，如果要重用套接字，请使用disconnectFromHost()，否则close()

关于3.和4：您正在执行的操作是在用户单击“连接”时创建ClientForTest，并在单击断开连接后立即将其删除。但那没有好的设计（恕我直言）。由于tcpSockForTest已经是类的成员，因此在构造函数中创建它（通过new），并在析构函数中删除它（可选地，因为如果您将小部件作为父级传递，Qt将为您删除它）。

断开连接Qt

1 个答案: