QTcpSocket类的方法connectToHost会泄露内存,即使把调用这个方法的QTcpSocket实例delete掉,内存也不会释放!反复connectToHost会导致段错误,十分危险。必须控制connectToHost的使用次数!
连接服务器
m_tcpSocket->connectToHost(“127.0.0.1”, 9877);
connected = m_tcpSocket->waitForConnected();
只有使用waitForConnected()后,QTcpSocket才真正尝试连接服务器,并返回是否连接的结果。
写数据
m_tcpSocket->write(str.toStdString().c_str(), strlen(str.toStdString().c_str()));
m_tcpSocket->waitForBytesWritten();
当使用waitForBytesWritten()后,QTcpSocket才真正发送数据。
m_tcpSocket->write(str1.toStdString().c_str(), strlen(str1.toStdString().c_str()));
m_tcpSocket->write(str2.toStdString().c_str(), strlen(str2.toStdString().c_str()));
的结果是发送了str1str2
断开与服务器的连接
m_tcpSocket->disconnectFromHost()
m_tcpSocket->waitForDisconnected()
善于使用QTcpSocket的SIGNAL:connected(),disconnected(),error(QAbstractSocket::SocketError)
配合自定义私有开关变量bool connected,QTimer可以实现自动重连接等逻辑。
QTcpSocket调试经验分享
这久在写一个基于TCP的通信程序,Server端用WinCE实现,而Client端用Qt实现,之前已写了一个VC的Client端,能正确向Server发送数据。
将Client端改用Qt实现后connectToHost()后,server端已能正确accept(),但就是write()后server的read函数无法响应。调试了半天没有成功,火大呀!今天试着输出socket的状态后得到如下:
bool TcpClient::newConnect(const QString &iAddr, quint16 iPort)
{
mSocket = newQTcpSocket(this);
mSocket->connectToHost(iAddr,iPort);
qDebug(“State:%d\n”,mSocket->state()); // State: 2; 2代表ConnectingState,正确的应该为3(ConnectedState)
connect(mSocket,SIGNAL(readyRead()),this,SLOT(read()));
connect(mSocket,SIGNAL(disconnected()),this,SLOT(disConnect()));return(true);
}
qint64 TcpClient::write(const QByteArray &iData)
{
qint64len = mSocket->write(iData);
qDebug(“State:%d\n”,mSocket->state()); // State: 2; 2代表ConnectingState,正确的应该为3(ConnectedState)
msleep(200);
return(len);
}
通过输出状态,已经找到问题的所在,哎!都是业务不熟害的呀!
socket的连接是异步的,所以必须等连接建立完成才能使用,所以分别加入waitForConnected()和waitForBytesWritten()后调试通过。
bool TcpClient::newConnect(const QString &iAddr, quint16 iPort)
{
mSocket = newQTcpSocket(this);
mSocket->connectToHost(iAddr, iPort);
qDebug(“State:%d\n”,mSocket->state()); // State: 2; 2代表ConnectingState,正确的应该为3(ConnectedState)
constintTimeout=5*1000;
if(!mSocket->waitForConnected(Timeout))
{
return(false);
}
qDebug("State:%d\n",mSocket>state()); // State: 3(ConnectedState)正确
connect(mSocket,SIGNAL(readyRead()),this,SLOT(read()));
connect(mSocket,SIGNAL(disconnected()),this,SLOT(disConnect()));return(true);
}
qint64 TcpClient::write(const QByteArray &iData)
{
qint64len = mSocket->write(iData);
mSocket->waitForBytesWritten(300);
qDebug(“State:%d\n”,mSocket->state()); // State: 3(ConnectedState)正确
msleep(200);
return(len);
}
转载自:http://blog.sina.com.cn/s/blog_4888f88101014euy.html#cmt_2022332