Detailed Description
The QFtp class provides an implementation of the FTP protocol.
This class provides two different interfaces: one is the
QNetworkProtocol interface that allows you to use FTP through the
QUrlOperator abstraction. The other is a direct interface to FTP
that gives you lower-level access to the FTP protocol for finer
control. Using the direct interface you can also execute arbitrary
FTP commands.
Don't mix the two interfaces, since the behavior is not
well-defined.
If you want to use QFtp with the QNetworkProtocol interface, you
do not use it directly, but rather through a QUrlOperator, for
example:
QUrlOperator op( "ftp://ftp.trolltech.com" );
op.listChildren(); // Asks the server to provide a directory listing
This code will only work if the QFtp class is registered; to
register the class, you must call qInitNetworkProtocols() before
using a QUrlOperator with QFtp.
The rest of this descrption describes the direct interface to FTP.
The class works asynchronously, so there are no blocking
functions. If an operation cannot be executed immediately, the
function will still return straight away and the operation will be
scheduled for later execution. The results of scheduled operations
are reported via signals. This approach depends on the event loop
being in operation.
The operations that can be scheduled (they are called "commands"
in the rest of the documentation) are the following:
connectToHost(), login(), close(), list(), cd(), get(), put(),
remove(), mkdir(), rmdir(), rename() and rawCommand().
All of these commands return a unique identifier that allows you
to keep track of the command that is currently being executed.
When the execution of a command starts, the commandStarted()
signal with the command's identifier is emitted. When the command
is finished, the commandFinished() signal is emitted with the
command's identifier and a bool that indicates whether the command
finished with an error.
In some cases, you might want to execute a sequence of commands,
e.g. if you want to connect and login to a FTP server. This is
simply achieved:
QFtp *ftp = new QFtp( this ); // this is an optional QObject parent
ftp->connectToHost( "ftp.trolltech.com" );
ftp->login();
In this case two FTP commands have been scheduled. When the last
scheduled command has finished, a done() signal is emitted with
a bool argument that tells you whether the sequence finished with
an error.
If an error occurs during the execution of one of the commands in
a sequence of commands, all the pending commands (i.e. scheduled,
but not yet executed commands) are cleared and no signals are
emitted for them.
Some commands, e.g. list(), emit additional signals to report
their results.
Example: If you want to download the INSTALL file from Trolltech's
FTP server, you would write this:
ftp->connectToHost( "ftp.trolltech.com" ); // id == 1
ftp->login(); // id == 2
ftp->cd( "qt" ); // id == 3
ftp->get( "INSTALL" ); // id == 4
ftp->close(); // id == 5
For this example the following sequence of signals is emitted
(with small variations, depending on network traffic, etc.):
start( 1 )
stateChanged( HostLookup )
stateChanged( Connecting )
stateChanged( Connected )
finished( 1, FALSE )
start( 2 )
stateChanged( LoggedIn )
finished( 2, FALSE )
start( 3 )
finished( 3, FALSE )
start( 4 )
dataTransferProgress( 0, 3798 )
dataTransferProgress( 2896, 3798 )
readyRead()
dataTransferProgress( 3798, 3798 )
readyRead()
finished( 4, FALSE )
start( 5 )
stateChanged( Closing )
stateChanged( Unconnected )
finished( 5, FALSE )
done( FALSE )
The dataTransferProgress() signal in the above example is useful
if you want to show a progressbar to
inform the user about the progress of the download. The
readyRead() signal tells you that there is data ready to be read.
The amount of data can be queried then with the bytesAvailable()
function and it can be read with the readBlock() or readAll()
function.
If the login fails for the above example, the signals would look
like this:
start( 1 )
stateChanged( HostLookup )
stateChanged( Connecting )
stateChanged( Connected )
finished( 1, FALSE )
start( 2 )
finished( 2, TRUE )
done( TRUE )
You can then get details about the error with the error() and
errorString() functions.
The functions currentId() and currentCommand() provide more
information about the currently executing command.
The functions hasPendingCommands() and clearPendingCommands()
allow you to query and clear the list of pending commands.
The safest and easiest way to use the FTP protocol is to use
QUrlOperator() or the FTP commands described above. If you are an
experienced network programmer and want to have complete control
you can use rawCommand() to execute arbitrary FTP commands.
See also Qt Network Documentation, QNetworkProtocol, QUrlOperator, QHttp, and Input/Output and Networking.
Member Type Documentation
QFtp::Command
This enum is used as the return value for the currentCommand() function.
This allows you to perform specific actions for particular
commands, e.g. in a FTP client, you might want to clear the
directory view when a list() command is started; in this case you
can simply check in the slot connected to the start() signal if
the currentCommand() is List.
- QFtp::None - No command is being executed.
- QFtp::ConnectToHost - connectToHost() is being executed.
- QFtp::Login - login() is being executed.
- QFtp::Close - close() is being executed.
- QFtp::List - list() is being executed.
- QFtp::Cd - cd() is being executed.
- QFtp::Get - get() is being executed.
- QFtp::Put - put() is being executed.
- QFtp::Remove - remove() is being executed.
- QFtp::Mkdir - mkdir() is being executed.
- QFtp::Rmdir - rmdir() is being executed.
- QFtp::Rename - rename() is being executed.
- QFtp::RawCommand - rawCommand() is being executed.
See also currentCommand().
QFtp::Error
This enum identifies the error that occurred.
- QFtp::NoError - No error occurred.
- QFtp::HostNotFound - The host name lookup failed.
- QFtp::ConnectionRefused - The server refused the connection.
- QFtp::NotConnected - Tried to send a command, but there is no connection to
a server.
- QFtp::UnknownError - An error other than those specified above
occurred.
See also error().
QFtp::State
This enum defines the connection state:
- QFtp::Unconnected - There is no connection to the host.
- QFtp::HostLookup - A host name lookup is in progress.
- QFtp::Connecting - An attempt to connect to the host is in progress.
- QFtp::Connected - Connection to the host has been achieved.
- QFtp::LoggedIn - Connection and user login have been achieved.
- QFtp::Closing - The connection is closing down, but it is not yet
closed. (The state will be Unconnected when the connection is
closed.)
See also stateChanged() and state().
Member Function Documentation
QFtp::QFtp ()
Constructs a QFtp object.
QFtp::QFtp ( QObject * parent, const char * name = 0 )
Constructs a QFtp object. The parent and name parameters
are passed to the QObject constructor.
QFtp::~QFtp () [virtual]
Destructor.
void QFtp::abort () [slot]
Aborts the current command and deletes all scheduled commands.
If there is an unfinished command (i.e. a command for which the
commandStarted() signal has been emitted, but for which the
commandFinished() signal has not been emitted), this function
sends an ABORT command to the server. When the server replies
that the command is aborted, the commandFinished() signal with the
error argument set to TRUE is emitted for the command. Due
to timing issues, it is possible that the command had already
finished before the abort request reached the server, in which
case, the commandFinished() signal is emitted with the error
argument set to FALSE.
For all other commands that are affected by the abort(), no
signals are emitted.
If you don't start further FTP commands directly after the
abort(), there won't be any scheduled commands and the done()
signal is emitted.
Warning: Some FTP servers, for example the BSD FTP daemon (version
0.3), wrongly return a positive reply even when an abort has
occurred. For these servers the commandFinished() signal has its
error flag set to FALSE, even though the command did not
complete successfully.
See also clearPendingCommands().
Example: network/ftpclient/ftpmainwindow.ui.h.
Q_ULONG QFtp::bytesAvailable () const
Returns the number of bytes that can be read from the data socket
at the moment.
See also get(), readyRead(), readBlock(), and readAll().
int QFtp::cd ( const QString & dir )
Changes the working directory of the server to dir.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also commandStarted() and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::clearPendingCommands ()
Deletes all pending commands from the list of scheduled commands.
This does not affect the command that is being executed. If you
want to stop this this as well, use abort().
See also hasPendingCommands() and abort().
int QFtp::close ()
Closes the connection to the FTP server.
The stateChanged() signal is emitted when the state of the
connecting process changes, e.g. to Closing, then Unconnected.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also stateChanged(), commandStarted(), and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::commandFinished ( int id, bool error ) [signal]
This signal is emitted when processing the command identified by
id has finished. error is TRUE if an error occurred during
the processing; otherwise error is FALSE.
See also commandStarted(), done(), error(), and errorString().
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::commandStarted ( int id ) [signal]
This signal is emitted when processing the command identified by
id starts.
See also commandFinished() and done().
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::connectToHost ( const QString & host, Q_UINT16 port = 21 )
Connects to the FTP server host using port port.
The stateChanged() signal is emitted when the state of the
connecting process changes, e.g. to HostLookup, then Connecting, then Connected.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also stateChanged(), commandStarted(), and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
Command QFtp::currentCommand () const
Returns the command type of the FTP command being executed or None if there is no command being executed.
See also currentId().
Example: network/ftpclient/ftpmainwindow.ui.h.
QIODevice * QFtp::currentDevice () const
Returns the QIODevice pointer that is used by the FTP command to read data
from or store data to. If there is no current FTP command being executed or
if the command does not use an IO device, this function returns 0.
This function can be used to delete the QIODevice in the slot connected to
the commandFinished() signal.
See also get() and put().
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::currentId () const
Returns the identifier of the FTP command that is being executed
or 0 if there is no command being executed.
See also currentCommand().
void QFtp::dataTransferProgress ( int done, int total ) [signal]
This signal is emitted in response to a get() or put() request to
indicate the current progress of the download or upload.
done is the amount of data that has already been transferred
and total is the total amount of data to be read or written. It
is possible that the QFtp class is not able to determine the total
amount of data that should be transferred, in which case total
is 0. (If you connect this signal to a QProgressBar, the progress
bar shows a busy indicator if the total is 0).
Warning: done and total are not necessarily the size in
bytes, since for large files these values might need to be
"scaled" to avoid overflow.
See also get(), put(), and QProgressBar::progress.
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::done ( bool error ) [signal]
This signal is emitted when the last pending command has finished;
(it is emitted after the last command's commandFinished() signal).
error is TRUE if an error occurred during the processing;
otherwise error is FALSE.
See also commandFinished(), error(), and errorString().
Example: network/ftpclient/ftpmainwindow.ui.h.
Error QFtp::error () const
Returns the last error that occurred. This is useful to find out
what when wrong when receiving a commandFinished() or a done()
signal with the error argument set to TRUE.
If you start a new command, the error status is reset to NoError.
QString QFtp::errorString () const
Returns a human-readable description of the last error that
occurred. This is useful for presenting a error message to the
user when receiving a commandFinished() or a done() signal with
the error argument set to TRUE.
The error string is often (but not always) the reply from the
server, so it is not always possible to translate the string. If
the message comes from Qt, the string has already passed through
tr().
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::get ( const QString & file, QIODevice * dev = 0 )
Downloads the file file from the server.
If dev is 0, then the readyRead() signal is emitted when there
is data available to read. You can then read the data with the
readBlock() or readAll() functions.
If dev is not 0, the data is written directly to the device dev. Make sure that the dev pointer is valid for the duration
of the operation (it is safe to delete it when the
commandFinished() signal is emitted). In this case the readyRead()
signal is not emitted and you cannot read data with the
readBlcok or readAll() functions.
If you don't read the data immediately it becomes available, i.e.
when the readyRead() signal is emitted, it is still available
until the next command is started.
For example, if you want to present the data to the user as soon
as there is something available, connect to the readyRead() signal
and read the data immediately. On the other hand, if you only want
to work with the complete data, you can connect to the
commandFinished() signal and read the data when the get() command
is finished.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also readyRead(), dataTransferProgress(), commandStarted(), and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
bool QFtp::hasPendingCommands () const
Returns TRUE if there are any commands scheduled that have not yet
been executed; otherwise returns FALSE.
The command that is being executed is not considered as a
scheduled command.
See also clearPendingCommands(), currentId(), and currentCommand().
int QFtp::list ( const QString & dir = QString::null )
Lists the contents of directory dir on the FTP server. If dir is empty, it lists the contents of the current directory.
The listInfo() signal is emitted for each directory entry found.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also listInfo(), commandStarted(), and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::listInfo ( const QUrlInfo & i ) [signal]
This signal is emitted for each directory entry the list() command
finds. The details of the entry are stored in i.
See also list().
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::login ( const QString & user = QString::null, const QString & password = QString::null )
Logs in to the FTP server with the username user and the
password password.
The stateChanged() signal is emitted when the state of the
connecting process changes, e.g. to LoggedIn.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also commandStarted() and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::mkdir ( const QString & dir )
Creates a directory called dir on the server.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also commandStarted() and commandFinished().
int QFtp::put ( QIODevice * dev, const QString & file )
Reads the data from the IO device dev, and writes it to the
file called file on the server. The data is read in chunks from
the IO device, so this overload allows you to transmit large
amounts of data without the need to read all the data into memory
at once.
Make sure that the dev pointer is valid for the duration of the
operation (it is safe to delete it when the commandFinished() is
emitted).
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::put ( const QByteArray & data, const QString & file )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Writes the data data to the file called file on the server.
The progress of the upload is reported by the
dataTransferProgress() signal.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also dataTransferProgress(), commandStarted(), and commandFinished().
int QFtp::rawCommand ( const QString & command )
Sends the raw FTP command command to the FTP server. This is
useful for low-level FTP access. If the operation you wish to
perform has an equivalent QFtp function, we recommend using the
function instead of raw FTP commands since the functions are
easier and safer.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also rawCommandReply(), commandStarted(), and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::rawCommandReply ( int replyCode, const QString & detail ) [signal]
This signal is emitted in response to the rawCommand() function.
replyCode is the 3 digit reply code and detail is the text
that follows the reply code.
See also rawCommand().
Example: network/ftpclient/ftpmainwindow.ui.h.
Reads all the bytes available from the data socket and returns
them.
See also get(), readyRead(), bytesAvailable(), and readBlock().
Q_LONG QFtp::readBlock ( char * data, Q_ULONG maxlen )
Reads maxlen bytes from the data socket into data and
returns the number of bytes read. Returns -1 if an error occurred.
See also get(), readyRead(), bytesAvailable(), and readAll().
void QFtp::readyRead () [signal]
This signal is emitted in response to a get() command when there
is new data to read.
If you specify a device as the second argument in the get()
command, this signal is not emitted; instead the data is
written directly to the device.
You can read the data with the readAll() or readBlock() functions.
This signal is useful if you want to process the data in chunks as
soon as it becomes available. If you are only interested in the
complete data, just connect to the commandFinished() signal and
read the data then instead.
See also get(), readBlock(), readAll(), and bytesAvailable().
int QFtp::remove ( const QString & file )
Deletes the file called file from the server.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also commandStarted() and commandFinished().
Example: network/ftpclient/ftpmainwindow.ui.h.
int QFtp::rename ( const QString & oldname, const QString & newname )
Renames the file called oldname to newname on the server.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also commandStarted() and commandFinished().
int QFtp::rmdir ( const QString & dir )
Removes the directory called dir from the server.
The function does not block and returns immediately. The command
is scheduled, and its execution is performed asynchronously. The
function returns a unique identifier which is passed by
commandStarted() and commandFinished().
When the command is started the commandStarted() signal is
emitted. When it is finished the commandFinished() signal is
emitted.
See also commandStarted() and commandFinished().
State QFtp::state () const
Returns the current state of the object. When the state changes,
the stateChanged() signal is emitted.
See also State and stateChanged().
Example: network/ftpclient/ftpmainwindow.ui.h.
void QFtp::stateChanged ( int state ) [signal]
This signal is emitted when the state of the connection changes.
The argument state is the new state of the connection; it is
one of the State values.
It is usually emitted in response to a connectToHost() or close()
command, but it can also be emitted "spontaneously", e.g. when the
server closes the connection unexpectedly.
See also connectToHost(), close(), state(), and State.
Example: network/ftpclient/ftpmainwindow.ui.h.
This file is part of the Qt toolkit.
Copyright © 1995-2003
Trolltech. All Rights Reserved.
