qt 链接 ftp服务器

可以使用Qt的QNetworkAccessManager类来链接FTP服务器。下面是一个简单的示例代码，可以用于连接FTP服务器并下载文件：

#include <QCoreApplication>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QUrl>
#include <QFile>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QNetworkAccessManager manager;
    QUrl url("ftp://example.com/file.txt");
    url.setUserName("username");
    url.setPassword("password");

    QNetworkReply *reply = manager.get(QNetworkRequest(url));
    QEventLoop loop;
    QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
    loop.exec();

    if (reply->error() == QNetworkReply::NoError) {
        QFile file("file.txt");
        if (file.open(QIODevice::WriteOnly)) {
            file.write(reply->readAll());
            file.close();
        }
    }

    reply->deleteLater();

    return a.exec();
}

需要注意的是，Qt默认情况下不支持FTP协议，需要在.pro文件中添加以下语句：

QT += network
CONFIG += ftp