qt访问ftp服务器

### 使用 Qt 访问 FTP 服务器 #### 下载文件 为了使用Qt访问FTP服务器并下载文件，可以利用`QNetworkAccessManager`来发起请求。下面是一个简单的例子展示如何连接至FTP服务器并获取文件： ```cpp #include <QCoreApplication> #include <QUrl> #include <QFile> #include <QNetworkRequest> #include <QNetworkReply> void downloadFile(const QString &urlString, const QString &destinationPath){ QNetworkAccessManager *manager = new QNetworkAccessManager(); connect(manager,SIGNAL(finished(QNetworkReply*)),this,SLOT(replyFinished(QNetworkReply*))); QFile *file = new QFile(destinationPath); file->open(QIODevice::WriteOnly); QUrl url(urlString); QNetworkRequest request(url); manager->get(request)->setParent(file); // Ensure the reply is deleted when done } // Slot to handle finished downloads. void replyFinished(QNetworkReply *reply) { if (reply->error() != QNetworkReply::NoError) { qDebug()<<"Download failed"; return; } QByteArray data=reply->readAll(); QFile *file = qobject_cast<QFile*>(reply->parent()); if (!file || !file->write(data)) { qDebug()<<"Failed to write downloaded content."; } else { qDebug()<<"Download succeeded!"; } file->close(); } ``` 这段代码展示了基本流程：创建`QNetworkAccessManager`实例用于发送HTTP(S)/FTP请求；通过`connect()`函数设置信号槽机制监听完成事件；定义处理程序保存接收到的数据到本地磁盘。 对于更复杂的交互比如上传文件，则可以通过调整方法调用来适应不同场景的需求[^1]。 #### 上传文件 当涉及到向FTP站点提交数据时，同样依赖于`QNetworkAccessManager`组件的功能。这里给出一段示范性的C++源码片段说明怎样把本地资源推送上去： ```cpp bool uploadFileToFTPServer(QString localFilePath,QString remoteDir,QObject *parent) { bool success=false; QFileInfo fileInfo(localFilePath); QString fileName=fileInfo.fileName(); QHttpMultiPart *multiPart=new QHttpMultiPart(QHttpMultiPart::FormDataType,parent); QHttpPart textPart; textPart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"path\"")); textPart.setBody(remoteDir.toUtf8()); multiPart->append(textPart); QHttpPart imagePart; imagePart.setHeader(QNetworkRequest::ContentTypeHeader, QVariant("image/jpeg")); // Adjust MIME type as necessary imagePart.setHeader(QNetworkRequest::ContentDispositionHeader, QVariant("form-data; name=\"upload\"; filename=\"" + fileName + "\"")); QFile *file=new QFile(localFilePath,parent); if(!file->exists()){ delete multiPart; return false; } if(!file->open(QIODevice::ReadOnly)){ delete multiPart; return false; } imagePart.setBodyDevice(file); file->setParent(multiPart); // we cannot delete the file now, so delete it with the multiPart multiPart->append(imagePart); QUrl targetUrl="ftp://username:[email protected]/"+remoteDir+"/"+fileName; QNetworkRequest req(targetUrl); QNetworkAccessManager *networkAccessManager=new QNetworkAccessManager(parent); QNetworkReply *reply=networkAccessManager->put(req,multiPart); multiPart->setParent(reply); QObject::connect(reply,&QNetworkReply::finished,[&]()mutable{ if(reply->error()==QNetworkReply::NoError){ qDebug()<<"Upload successful!"; success=true; }else{ qDebug()<< "Upload error:"<<reply->errorString(); } reply->deleteLater(); }); return success; } ``` 此部分实现了构造多部件消息体以携带待传送的内容，并指定了目标URL（含认证信息）。注意这里的MIME类型应依据实际文件格式做相应更改[^2]。