if(myCom!=NULL){ myCom->close(); myCom->setParent(NULL); delete myCom; myCom=NULL; } myCom = new Win_QextSerialPort(portData.Com,QextSerialBase::EventDriven);如上可以在打开时判断是否已经创建串口类指针myCom，如果指针不为空，先关闭串口然后释放指针，最后重新创建指针即可。
会出现close（）方法无法调用问题，需要将方法中
// if (QThread::currentThread() != overlapThread)// overlapThread->wait();两句屏蔽掉，如下。
void Win_QextSerialPort::close()
{
LOCK_MUTEX();
if (isOpen()) {
flush();
if (overlapThread->isRunning()) {
overlapThread->stop();
// if (QThread::currentThread() != overlapThread)
// overlapThread->wait();
}
if (CloseHandle(Win_Handle))
Win_Handle = INVALID_HANDLE_VALUE;
_bytesToWrite = 0;
QIODevice::close();
}
UNLOCK_MUTEX();
}