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<td width="1"> </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="functions.html"><font color="#004faf">All Functions</font></a> · <a href="overviews.html"><font color="#004faf">Overviews</font></a></td></tr></table><h1 class="title">FTP Example<br /><span class="subtitle"></span>
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<p>Files:</p>
<ul>
<li><a href="network-qftp-ftpwindow-cpp.html">network/qftp/ftpwindow.cpp</a></li>
<li><a href="network-qftp-ftpwindow-h.html">network/qftp/ftpwindow.h</a></li>
<li><a href="network-qftp-sym-iap-util-h.html">network/qftp/sym_iap_util.h</a></li>
<li><a href="network-qftp-main-cpp.html">network/qftp/main.cpp</a></li>
<li><a href="network-qftp-ftp-qrc.html">network/qftp/ftp.qrc</a></li>
<li><a href="network-qftp-qftp-pro.html">network/qftp/qftp.pro</a></li>
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<p>Images:</p>
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<li><a href="images/used-in-examples/network/qftp/images/cdtoparent.png">network/qftp/images/cdtoparent.png</a></li>
<li><a href="images/used-in-examples/network/qftp/images/dir.png">network/qftp/images/dir.png</a></li>
<li><a href="images/used-in-examples/network/qftp/images/file.png">network/qftp/images/file.png</a></li>
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<p>The FTP example demonstrates a simple FTP client that can be used to list the available files on an FTP server and download them.</p>
<p align="center"><img src="images/ftp-example.png" /></p><p>The user of the example can enter the address or hostname of an FTP server in the <b>Ftp Server</b> line edit, and then push the <b>Connect</b> button to connect to it. A list of the server's top-level directory is then presented in the <b>File List</b> tree view. If the selected item in the view is a file, the user can download it by pushing the <b>Download</b> button. An item representing a directory can be double clicked with the mouse to show the contents of that directory in the view.</p>
<p>The functionality required for the example is implemented in the <a href="qftp.html">QFtp</a> class, which provides an easy, high-level interface to the file transfer protocol. FTP operations are requested through <a href="qftp.html#Command-enum">QFtp::Command</a>s. The operations are asynchronous. <a href="qftp.html">QFtp</a> will notify us through signals when commands are started and finished.</p>
<p>We have one class, <tt>FtpWindow</tt>, which sets up the GUI and handles the FTP functionality. We will now go through its definition and implementation - focusing on the code concerning FTP. The code for managing the GUI is explained in other examples.</p>
<a name="ftpwindow-class-definition"></a>
<h2>FtpWindow Class Definition</h2>
<p>The <tt>FtpWindow</tt> class displays a window, in which the user can connect to and browse the contents of an FTP server. The slots of <tt>FtpWindow</tt> are connected to its widgets, and contain the functionality for managing the FTP connection. We also connect to signals in <a href="qftp.html">QFtp</a>, which tells us when the <a href="qftp.html#Command-enum">commands</a> we request are finished, the progress of current commands, and information about files on the server.</p>
<pre> private slots:
void connectOrDisconnect();
void downloadFile();
void cancelDownload();
void ftpCommandFinished(int commandId, bool error);
void addToList(const QUrlInfo &urlInfo);
void processItem(QTreeWidgetItem *item, int column);
void cdToParent();
void updateDataTransferProgress(qint64 readBytes,
qint64 totalBytes);
void enableDownloadButton();</pre>
<p>We will look at each slot when we examine the <tt>FtpWindow</tt> implementation in the next section. We also make use of a few private variables:</p>
<pre> QHash<QString, bool> isDirectory;
QString currentPath;
QFtp *ftp;
QFile *file;
#ifdef Q_OS_SYMBIAN
bool bDefaultIapSet;
#endif</pre>
<p>The <tt>isDirectory</tt> hash keeps a history of all entries explored on the FTP server, and registers whether an entry represents a directory or a file. We use the <a href="qfile.html">QFile</a> object to download files from the FTP server.</p>
<a name="ftpwindow-class-implementation"></a>
<h2>FtpWindow Class Implementation</h2>
<p>We skip the <tt>FtpWindow</tt> constructor as it only contains code for setting up the GUI, which is explained in other examples.</p>
<p>We move on to the slots, starting with <tt>connectOrDisconnect()</tt>.</p>
<pre> void FtpWindow::connectOrDisconnect()
{
#ifdef Q_OS_SYMBIAN
if(!bDefaultIapSet) {
qt_SetDefaultIap();
bDefaultIapSet = true;
}
#endif
if (ftp) {
ftp->abort();
ftp->deleteLater();
ftp = 0;</pre>
<p>If <tt>ftp</tt> is already pointing to a <a href="qftp.html">QFtp</a> object, we <a href="qftp.html#Command-enum">QFtp::Close</a> its FTP connection and delete the object it points to. Note that we do not delete the object using standard C++ <tt>delete</tt> as we need it to finish its abort operation.</p>
<pre> ...
ftp = new QFtp(this);
connect(ftp, SIGNAL(commandFinished(int,bool)),
this, SLOT(ftpCommandFinished(int,bool)));
connect(ftp, SIGNAL(listInfo(QUrlInfo)),
this, SLOT(addToList(QUrlInfo)));
connect(ftp, SIGNAL(dataTransferProgress(qint64,qint64)),
this, SLOT(updateDataTransferProgress(qint64,qint64)));
fileList->clear();
currentPath.clear();
isDirectory.clear();</pre>
<p>If we get here, <tt>connectOrDisconnect()</tt> was called to establish a new FTP connection. We create a new <a href="qftp.html">QFtp</a> for our new connection, and connect its signals to slots in <tt>FtpWindow</tt>. The <a href="qftp.html#listInfo">listInfo()</a> signal is emitted whenever information about a single file on the sever has been resolved. This signal is sent when we ask <a href="qftp.html">QFtp</a> to <a href="qftp.html#list">list()</a> the contents of a directory. Finally, the <a href="qftp.html#dataTransferProgress">dataTransferProgress()</a> signal is emitted repeatedly during an FTP file transfer, giving us progress reports.</p>
<pre> QUrl url(ftpServerLineEdit->text());
if (!url.isValid() || url.scheme().toLower() != QLatin1String("ftp")) {
ftp->connectToHost(ftpServerLineEdit->text(), 21);
ftp->login();
} else {
ftp->connectToHost(url.host(), url.port(21));
if (!url.userName().isEmpty())
ftp->login(QUrl::fromPercentEncoding(url.userName().toLatin1()), url.password());
else
ftp->login();
if (!url.path().isEmpty())
ftp->cd(url.path());
}</pre>
<p>The <b>Ftp Server</b> line edit contains the IP address or hostname of the server to which we want to connect. We first check that the URL is a valid FTP sever address. If it isn't, we still try to connect using the plain text in <tt>ftpServerLineEdit</tt>. In either case, we assume that port <tt>21</tt> is used.</p>
<p>If the URL does not contain a user name and password, we use <a href="qftp.html#login">QFtp::login</a>(), which will attempt to log into the FTP sever as an anonymous user. The <a href="qftp.html">QFtp</a> object will now notify us when it has connected to the FTP server; it will also send a signal if it fails to connect or the username and password were rejected.</p>
<p>We move on to the <tt>downloadFile()</tt> slot:</p>
<pre> void FtpWindow::downloadFile()
{
QString fileName = fileList->currentItem()->text(0);
...
file = new QFile(fileName);
if (!file->open(QIODevice::WriteOnly)) {
QMessageBox::information(this, tr("FTP"),
tr("Unable to save the file %1: %2.")
.arg(fileName).arg(file->errorString()));
delete file;
return;
}
ftp->get(fileList->currentItem()->text(0), file);
progressDialog->setLabelText(tr("Downloading %1...").arg(fileName));
downloadButton->setEnabled(false);
progressDialog->exec();
}</pre>
<p>We first fetch the name of the file, which we find in the selected item of <tt>fileList</tt>. We then start the download by using <a href="qftp.html#get">QFtp::get</a>(). <a href="qftp.html">QFtp</a> will send progress signals during the download and a signal when the download is completed.</p>
<pre> void FtpWindow::cancelDownload()
{
ftp->abort();
}</pre>
<p><a href="qftp.html">QFtp</a> supports canceling the download of files.</p>
<pre> void FtpWindow::ftpCommandFinished(int, bool error)
{
#ifndef QT_NO_CURSOR
setCursor(Qt::ArrowCursor);
#endif
if (ftp->currentCommand() == QFtp::ConnectToHost) {
if (error) {
QMessageBox::information(this, tr("FTP"),
tr("Unable to connect to the FTP server "
"at %1. Please check that the host "
"name is correct.")
.arg(ftpServerLineEdit->text()));
connectOrDisconnect();
return;
}
statusLabel->setText(tr("Logged onto %1.")
.arg(ftpServerLineEdit->text()));
fileList->setFocus();
downloadButton->setDefault(true);
connectButton->setEnabled(true);
return;
}</pre>
<p>The <tt>ftpCommandFinished()</tt> slot is called when <a href="qftp.html">QFtp</a> has finished a <a href="qftp.html#Command-enum">QFtp::Command</a>. If an error occurred during the command, <a href="qftp.html">QFtp</a> will set <tt>error</tt> to one of the values in the <a href="qftp.html#Error-enum">QFtp::Error</a> enum; otherwise, <tt>error</tt> is zero.</p>
<pre> if (ftp->currentCommand() == QFtp::Login)
ftp->list();</pre>
<p>After login, the <a href="qftp.html#list">QFtp::list</a>() function will list the top-level directory on the server. addToList() is connected to <a href="qftp.html#listInfo">QFtp::listInfo</a>(), and will be invoked for each entry in that directory.</p>
<pre> if (ftp->currentCommand() == QFtp::Get) {
if (error) {
statusLabel->setText(tr("Canceled download of %1.")
.arg(file->fileName()));
file->close();
file->remove();
} else {
statusLabel->setText(tr("Downloaded %1 to current directory.")
.arg(file->fileName()));
file->close();
}
delete file;
enableDownloadButton();
progressDialog->hide();</pre>
<p>When a <a href="qftp.html#Command-enum">Get</a> command is finished, a file has finished downloading (or an error occurred during the download).</p>
<pre> } else if (ftp->currentCommand() == QFtp::List) {
if (isDirectory.isEmpty()) {
fileList->addTopLevelItem(new QTreeWidgetItem(QStringList() << tr("<empty>")));
fileList->setEnabled(false);
}
}</pre>
<p>After a <a href="qftp.html#Command-enum">List</a> command is performed, we have to check if no entries were found (in which case our <tt>addToList()</tt> function would not have been called).</p>
<p>Let's continue with the <tt>addToList()</tt> slot:</p>
<pre> void FtpWindow::addToList(const QUrlInfo &urlInfo)
{
QTreeWidgetItem *item = new QTreeWidgetItem;
item->setText(0, urlInfo.name());
item->setText(1, QString::number(urlInfo.size()));
item->setText(2, urlInfo.owner());
item->setText(3, urlInfo.group());
item->setText(4, urlInfo.lastModified().toString("MMM dd yyyy"));
QPixmap pixmap(urlInfo.isDir() ? ":/images/dir.png" : ":/images/file.png");
item->setIcon(0, pixmap);
isDirectory[urlInfo.name()] = urlInfo.isDir();
fileList->addTopLevelItem(item);
if (!fileList->currentItem()) {
fileList->setCurrentItem(fileList->topLevelItem(0));
fileList->setEnabled(true);
}
}</pre>
<p>When a new file has been resolved during a <a href="qftp.html#Command-enum">QFtp::List</a> command, this slot is invoked with a <a href="qurlinfo.html">QUrlInfo</a> describing the file. We create a separate row for the file in <tt>fileList</tt>. If <tt>fileList</tt> does not have a current item, we set the new item to be the current item.</p>
<pre> void FtpWindow::processItem(QTreeWidgetItem *item, int <span class="comment">/*column*/</span>)
{
QString name = item->text(0);
if (isDirectory.value(name)) {
fileList->clear();
isDirectory.clear();
currentPath += '/';
currentPath += name;
ftp->cd(name);
ftp->list();
cdToParentButton->setEnabled(true);
#ifndef QT_NO_CURSOR
setCursor(Qt::WaitCursor);
#endif
return;
}
}</pre>
<p>The <tt>processItem()</tt> slot is called when an item is double clicked in the <b>File List</b>. If the item represents a directory, we want to load the contents of that directory with <a href="qftp.html#list">QFtp::list</a>().</p>
<pre> void FtpWindow::cdToParent()
{
#ifndef QT_NO_CURSOR
setCursor(Qt::WaitCursor);
#endif
fileList->clear();
isDirectory.clear();
currentPath = currentPath.left(currentPath.lastIndexOf('/'));
if (currentPath.isEmpty()) {
cdToParentButton->setEnabled(false);
ftp->cd("/");
} else {
ftp->cd(currentPath);
}
ftp->list();
}</pre>
<p><tt>cdToParent()</tt> is invoked when the user requests to go to the parent directory of the one displayed in the file list. After changing the directory, we <a href="qftp.html#Command-enum">QFtp::List</a> its contents.</p>
<pre> void FtpWindow::updateDataTransferProgress(qint64 readBytes,
qint64 totalBytes)
{
progressDialog->setMaximum(totalBytes);
progressDialog->setValue(readBytes);
}</pre>
<p>The <tt>updateDataTransferProgress()</tt> slot is called regularly by <a href="qftp.html#dataTransferProgress">QFtp::dataTransferProgress</a>() when a file download is in progress. We use a <a href="qprogressdialog.html">QProgressDialog</a> to show the download progression to the user.</p>
<pre> void FtpWindow::enableDownloadButton()
{
QTreeWidgetItem *current = fileList->currentItem();
if (current) {
QString currentFile = current->text(0);
downloadButton->setEnabled(!isDirectory.value(currentFile));
} else {
downloadButton->setEnabled(false);
}
}</pre>
<p>The <tt>enableDownloadButton()</tt> is called whenever the current item in <tt>fileList</tt> changes. If the item represents a file, the <b>Enable Download</b> Button should be enabled; otherwise, it is disabled.</p>
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