QSocket(3qt)QSocket(3qt)NAMEQSocket - Buffered TCP connection
#include <qsocket.h>
Inherits QIODevice and QObject.
Public Members
enum Error { ErrConnectionRefused, ErrHostNotFound,
ErrSocketRead }
QSocket ( QObject * parent=0, const char * name=0 )
virtual ~QSocket ()
enum State { Idle, HostLookup, Connecting, Listening,
Connection, Closing }
State state () const
int socket () const
virtual void setSocket ( int )
virtual void connectToHost ( const QString & host,
Q_UINT16 port )
QString peerName () const
virtual bool open ( int mode )
virtual void close ()
virtual void flush ()
virtual uint size () const
virtual int at () const
virtual bool at ( int )
virtual bool atEnd () const
int bytesAvailable () const
int waitForMore ( int msecs ) const
int bytesToWrite () const
virtual int readBlock ( char * data, uint maxlen )
virtual int writeBlock ( const char * data, uint len )
virtual int getch ()
virtual int putch ( int )
virtual int ungetch ( int )
bool canReadLine () const
virtual QString readLine ()
Q_UINT16 port () const
Q_UINT16 peerPort () const
QHostAddress address () const
QHostAddress peerAddress () const
Signals
void hostFound ()
void connected ()
void connectionClosed ()
void delayedCloseFinished ()
void readyRead ()
void bytesWritten ( int nbytes )
void error ( int )
Protected Members
QSocketDevice* socketDevice ()
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QSocket(3qt)QSocket(3qt)
Protected Slots
virtual void sn_read ()
virtual void sn_write ()
DESCRIPTION
The QSocket class provides a buffered TCP connection.
It provides a totally non-blocking QIODevice, and modifies
and extends the API of QIODevice with socket-specific
code.
The functions you're likely to call most are
connectToHost(), bytesAvailable(), canReadLine() and the
ones it inherits from QIODevice.
connectToHost() is the most-used function. As its name
implies, it opens a connection to a named host.
Most network protocols are either packet-oriented or line-
oriented. canReadLine() indicates whether a connection
contains an entire unread line or not, and
bytesAvailable() returns the number of bytes available for
reading.
The signals error(), connected(), readyRead() and
connectionClosed() inform you of the progress of the
connection. There are also some less commonly used
signals. hostFound() is emitted when connectToHost() has
finished its DSN lookup and is starting its TCP
connection. delayedCloseFinished() is emitted when close()succeeds(). bytesWritten() is emitted when QSocket moves
data from its "to be written" queue into the TCP
implementation.
There are several access functions for the socket: state()
returns whether the object is idle, is doing a DNS lookup,
is connecting, has an operational connection, etc.
address() and port() return the IP address and port used
for the connection, peerAddress() and peerPort() return
the IP address and port used by the peer, and peerName()
returns the name of the peer (normally the name that was
passed to connectToHost()). socket() returns a pointer to
the QSocketDevice used for this socket.
QSocket inherits QIODevice, and reimplements some of the
functions. In general, you can treat it as a QIODevice for
writing, and mostly also for reading. The match isn't
perfect, since the QIODevice API is designed for devices
that are controlled by the same machine, and an
asynchronous peer-to-peer network connection isn't quite
like that. For example, there is nothing that matches
QIODevice::size() exactly. The documentation for each of
open(), close(), flush(), size(), at(), atEnd(),
readBlock(), writeBlock(), getch(), putch(), ungetch() and
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See also QSocketDevice, QHostAddress and QSocketNotifier.
Member Type Documentation
QSocket::Error
This enum specifies the possible errors:
QSocket::ErrConnectionRefused if the connection was
refused
QSocket::ErrHostNotFound if the host was not found
QSocket::ErrSocketRead if a read from the socket failed
QSocket::State
This enum defines the connection states:
QSocket::Idle if there is no connection
QSocket::HostLookup during a DNS lookup
QSocket::Connecting during TCP connection establishment
QSocket::Connection when there is an operational
connection
QSocket::Closing if the socket is closing down, but is not
yet closed.
MEMBER FUNCTION DOCUMENTATIONQSocket::QSocket ( QObject * parent=0, const char * name=0 )
Creates a QSocket object in QSocket::Idle state.
QSocket::~QSocket () [virtual]
Destructs the socket. Closes the connection if necessary.
See also close().
QHostAddress QSocket::address () const
Returns the host address of this socket. (This is normally
be the main IP address of the host, but can be e.g.
127.0.0.1 for connections to localhost.).
bool QSocket::at ( int index ) [virtual]
Moves the read index forward and returns TRUE if the
operation was successful. Moving the index forward means
skipping incoming data.
Reimplemented from QIODevice.
int QSocket::at () const [virtual]
Returns the current read index. Since QSocket is a
sequential device, the current read index is always zero.
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Reimplemented from QIODevice.
bool QSocket::atEnd () const [virtual]
Returns TRUE if there is no more data to read, otherwise
FALSE.
Reimplemented from QIODevice.
int QSocket::bytesAvailable () const
Returns the number of incoming bytes that can be read,
i.e. the size of the input buffer. Equivalent to size().
See also bytesToWrite().
int QSocket::bytesToWrite () const
Returns the number of bytes that are waiting to be
written, i.e. the size of the output buffer.
See also bytesAvailable().
void QSocket::bytesWritten ( int nbytes ) [signal]
This signal is emitted when data actually has been written
to the network. The nbytes parameter says how many bytes
were written.
The bytesToWrite() function is often used in the same
context, and it tells how many buffered bytes there are
left to write.
See also writeBlock() and bytesToWrite().
bool QSocket::canReadLine () const
Returns TRUE if it's possible to read an entire line of
text from this socket at this time, or FALSE if not.
See also setMode() and readLine().
void QSocket::close () [virtual]
Closes the socket.
The mode is set to QSocket::Binary and the read buffer is
cleared.
If the output buffer is empty, the state is set to
QSocket::Idle and the connection is terminated
immediately. If the output buffer still contains data to
be written, QSocket goes into the QSocket::Closing state
and the rest of the data will be written. When all of the
outgoing data have been written, the state is set to
QSocket::Idle and the connection is terminated. At this
point, the delayedCloseFinished() signal is emitted.
See also state(), setMode() and bytesToWrite().
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Reimplemented from QIODevice.
void QSocket::connectToHost ( const QString & host, Q_UINT16 port
) [virtual]
Attempts to make a connection to host on the specified
port and return immediately.
Any connection or pending connection is closed
immediately, and QSocket goes into HostLookup state. When
the lookup succeeds, it emits hostFound(), starts a TCP
connection and goes into Connecting state. Finally, when
the connection succeeds, it emits connected() and goes
into Connection state. If there is an error at any point,
it emits error().
See also state().
void QSocket::connected () [signal]
This signal is emitted after connectToHost() has been
called and a connection has been successfully established.
See also connectToHost() and connectionClosed().
void QSocket::connectionClosed () [signal]
This signal is emitted when the other end has closed the
connection. The read buffers may contain buffered input
data which you can read after the connection was closed.
See also connectToHost() and close().
void QSocket::delayedCloseFinished () [signal]
This signal is emitted when a delayed close is finished.
If you call close() and there is buffered output data to
be written, QSocket goes into the QSocket::Closing state
and returns immediately. It will then keep writing to the
socket until all the data has been written. Then, the
delayCloseFinished() signal is emitted.
See also close().
void QSocket::error ( int ) [signal]
This signal is emitted after an error occurred.
void QSocket::flush () [virtual]
Implementation of the abstract virtual QIODevice::flush()
function.
Reimplemented from QIODevice.
int QSocket::getch () [virtual]
Reads a single byte/character from the internal read
buffer. Returns the byte/character read, or -1 if there is
nothing to be read.
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See also bytesAvailable() and putch().
Reimplemented from QIODevice.
void QSocket::hostFound () [signal]
This signal is emitted after connectToHost() has been
called and the host lookup has succeeded.
See also connected().
bool QSocket::open ( int m ) [virtual]
Opens the socket using the specified QIODevice file mode.
This function is called automatically when needed and you
should not call it yourself.
See also close().
Reimplemented from QIODevice.
QHostAddress QSocket::peerAddress () const
Returns the host address as resolved from the name
specified to the connectToHost() function.
QString QSocket::peerName () const
Returns the host name as specified to the connectToHost()
function. An empty string is returned if none has been
set.
Q_UINT16 QSocket::peerPort () const
Returns the peer's host port number, normally as specified
to the connectToHost() function. If none has been set,
this function returns 0.
Q_UINT16 QSocket::port () const
Returns the host port number of this socket.
int QSocket::putch ( int ch ) [virtual]
Writes the character ch into the output buffer.
Returns ch, or -1 if some error occurred.
See also getch().
Reimplemented from QIODevice.
int QSocket::readBlock ( char * data, uint maxlen ) [virtual]
Reads max maxlen bytes from the socket into data and
returns the number of bytes read. Returns -1 if an error
occurred.
Reimplemented from QIODevice.
QString QSocket::readLine () [virtual]
Returns a line of text including a terminating newline
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character (\n). Returns "" if canReadLine() returns FALSE.
See also canReadLine().
int QSocket::readLine ( char * data, uint maxlen ) [virtual]
Reimplemented for internal reasons; the API is not
affected.
Reimplemented from QIODevice.
void QSocket::readyRead () [signal]
This signal is emitted when there is incoming data to be
read.
Every time when there is new incoming data this signal is
emitted once. Keep in mind that new incoming data is only
reported once; i.e. if you do not read all data, this
signal is not emitted again unless new data arrives on the
socket.
See also readBlock(), readLine() and bytesAvailable().
void QSocket::setSocket ( int socket ) [virtual]
Sets the socket to use socket and the state() to
Connected. The socket should already be connected.
This allows one to use the QSocket class as a wrapper for
other socket types (e.g. Unix Domain Sockets under Unix).
uint QSocket::size () const [virtual]
Returns the number of incoming bytes that can be read
right now (like bytesAvailable()).
Reimplemented from QIODevice.
void QSocket::sn_read () [virtual protected slot]
Internal slot for handling socket read notifications.
void QSocket::sn_write () [virtual protected slot]
Internal slot for handling socket write notifications.
int QSocket::socket () const
Returns the socket number, or -1 if there is no socket at
the moment.
QSocketDevice * QSocket::socketDevice () [protected]
Returns a pointer to the internal socket device. The
returned pointer may be null.
There is normally no need to manipulate the socket device
directly since this class does the necessary setup for
most applications.
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QSocket(3qt)QSocket(3qt)QSocket::State QSocket::state() const
Returns the current state of the socket connection.
See also QSocket::State.
int QSocket::ungetch ( int ) [virtual]
This implementation of the virtual function
QIODevice::ungetch() always returns -1 (error) because a
QSocket is a sequential device and does not allow any
ungetch operation.
Reimplemented from QIODevice.
int QSocket::waitForMore ( int msecs ) const
Wait upto msecs milliseconds for more data to be
available.
If msecs is -1 the call will block indefinitely. This is a
blocking call and should be avoided in event driven
applications.
Returns the number of bytes available.
See also bytesAvailable().
int QSocket::writeBlock ( const char * data, uint len ) [virtual]
Writes len bytes to the socket from data and returns the
number of bytes written. Returns -1 if an error occurred.
Reimplemented from QIODevice.
SEE ALSO
http://doc.trolltech.com/qsocket.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page (qsocket.3qt)
and the Qt version (2.3.1).
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