1. 头文件：

#include <windows.h>

#include <tlhelp32.h>

2. 发送方：

void sendMessage()
{
    // 根据窗口名称查找窗口句柄
    HWND hWnd = ::FindWindowA(("myWindowsName"), NULL);
    if (hWnd == nullptr) {
        return;
    }

    // 组装copydata信息
    std::string param = QString("UID=0\r\nCommand=ChangeCode\r\n").toStdString();
    COPYDATASTRUCT data;
    data.dwData = 0;
    data.cbData = param.length();
    data.lpData = &param[0];

    // 发送消息
    ::SendMessage(hWnd, WM_COPYDATA, (WPARAM)0, (LPARAM)&data);
}

3. 接收方：?

    bool nativeEvent(const QByteArray &eventType, void *message, long *result);//接收消息

bool xxxWidget::nativeEvent(const QByteArray &eventType, void *message, long *result)
{
    if (eventType == "windows_generic_MSG")
    {
        MSG* msg = reinterpret_cast<MSG*>(message);

        if(msg->message == WM_COPYDATA)
        {
            COPYDATASTRUCT *data = reinterpret_cast<COPYDATASTRUCT*>(msg->lParam);
            QTextCodec *gbk = QTextCodec::codecForName("GB18030");
            QString recevice = gbk->toUnicode((char *)(data->lpData));

             // 业务1
            if(recevice.contains("Command=openNewTab")) {
               //TODO  业务1处理
               
               return true;
            } else if(recevice.contains("Command=close")) {
                // TODO 业务2处理
            
                return true;
             }

            m_wnd = reinterpret_cast<HWND>(msg->wParam);
        }
    }
    return QWidget::nativeEvent(eventType, message, result);
}