Detailed Description
The QSocketDevice class provides a platform-independent low-level socket API.
This class provides a low level API for working with sockets. Users of
this class are assumed to have networking experience. For most users the
QSocket class provides a much easier and high level alternative, but
certain thing (like UDP) can't be done with QSocket and if you need a
platform-independent API for those, QSocketDevice is the right choice.
The essential purpose of the class is to provide a QIODevice that
works on sockets, wrapped in a platform-independent API.
See also QSocket, QSocketNotifier, QHostAddress, and Input/Output and Networking.
Member Type Documentation
QSocketDevice::Error
This enum type describes the error states of QSocketDevice.
QSocketDevice::Type
This enum type describes the type of the socket:
- QSocketDevice::Stream - a stream socket (TCP, usually)
- QSocketDevice::Datagram - a datagram socket (UDP, usually)
Member Function Documentation
QSocketDevice::QSocketDevice ( Type type = Stream )
Creates a QSocketDevice object for a stream or datagram socket.
The type argument must be either QSocketDevice::Stream for a
reliable, connection-oriented TCP socket, or QSocketDevice::Datagram for an unreliable UDP socket.
See also blocking().
QSocketDevice::QSocketDevice ( int socket, Type type )
Creates a QSocketDevice object for the existing socket socket.
The type argument must match the actual socket type; use QSocketDevice::Stream for a reliable, connection-oriented TCP
socket, or QSocketDevice::Datagram for an unreliable,
connectionless UDP socket.
QSocketDevice::~QSocketDevice () [virtual]
Destroys the socket device and closes the socket if it is open.
int QSocketDevice::accept () [virtual]
Extracts the first connection from the queue of pending
connections for this socket and returns a new socket identifier.
Returns -1 if the operation failed.
See also bind() and listen().
QHostAddress QSocketDevice::address () const
Returns the address of this socket device. This may be 0.0.0.0 for
a while, but is set to something sensible as soon as a sensible
value is available.
bool QSocketDevice::addressReusable () const
Returns TRUE if the address of this socket can be used by other
sockets at the same time, and FALSE if this socket claims
exclusive ownership.
See also setAddressReusable().
bool QSocketDevice::bind ( const QHostAddress & address, Q_UINT16 port ) [virtual]
Assigns a name to an unnamed socket. The name is the host address
address and the port number port. If the operation succeeds,
bind() returns TRUE; otherwise it returns FALSE without changing
what port() and address() return.
bind() is used by servers for setting up incoming connections.
Call bind() before listen().
bool QSocketDevice::blocking () const
Returns TRUE if the socket is valid and in blocking mode;
otherwise returns FALSE.
Note that this function does not set error().
Warning: On Windows, this function always returns TRUE since the
ioctlsocket() function is broken.
See also setBlocking() and isValid().
Q_LONG QSocketDevice::bytesAvailable () const
Returns the number of bytes available for reading, or -1 if an
error occurred.
Warning: On Microsoft Windows, we use the ioctlsocket() function
to determine the number of bytes queued on the socket. According
to Microsoft (KB Q125486), ioctlsocket() sometimes returns an
incorrect number. The only safe way to determine the amount of
data on the socket is to read it using readBlock(). QSocket has
workarounds to deal with this problem.
bool QSocketDevice::connect ( const QHostAddress & addr, Q_UINT16 port ) [virtual]
Connects to the IP address and port specified by addr and port. Returns TRUE if it establishes a connection; otherwise returns FALSE.
If it returns FALSE, error() explains why.
Note that error() commonly returns NoError for non-blocking
sockets; this just means that you can call connect() again in a
little while and it'll probably succeed.
Error QSocketDevice::error () const
Returns the first error seen.
bool QSocketDevice::isValid () const
Returns TRUE if this is a valid socket; otherwise returns FALSE.
See also socket().
bool QSocketDevice::listen ( int backlog ) [virtual]
Specifies how many pending connections a server socket can have.
Returns TRUE if the operation was successful; otherwise returns
FALSE. A backlog value of 50 is quite common.
The listen() call only applies to sockets where type() is Stream, i.e. not to Datagram sockets. listen() must not be
called before bind() or after accept().
See also bind() and accept().
QHostAddress QSocketDevice::peerAddress () const
Returns the address of the port this socket device is connected
to. This may be 0.0.0.0 for a while, but is set to something
sensible as soon as a sensible value is available.
Note that for Datagram sockets, this is the source port of the
last packet received.
Q_UINT16 QSocketDevice::peerPort () const
Returns the port number of the port this socket device is
connected to. This may be 0 for a while, but is set to something
sensible as soon as a sensible value is available.
Note that for Datagram sockets, this is the source port of the
last packet received, and that it is in native byte order.
Q_UINT16 QSocketDevice::port () const
Returns the port number of this socket device. This may be 0 for a
while, but is set to something sensible as soon as a sensible
value is available.
Note that Qt always uses native byte order, i.e. 67 is 67 in Qt;
there is no need to call htons().
Q_LONG QSocketDevice::readBlock ( char * data, Q_ULONG maxlen ) [virtual]
Reads maxlen bytes from the socket into data and returns the
number of bytes read. Returns -1 if an error occurred.
Reimplemented from QIODevice.
int QSocketDevice::receiveBufferSize () const
Returns the size of the operating system receive buffer.
See also setReceiveBufferSize().
int QSocketDevice::sendBufferSize () const
Returns the size of the operating system send buffer.
See also setSendBufferSize().
void QSocketDevice::setAddressReusable ( bool enable ) [virtual]
Sets the address of this socket to be usable by other sockets too
if enable is TRUE, and to be used exclusively by this socket if
enable is FALSE.
When a socket is reusable, other sockets can use the same port
number (and IP address), which is generally useful. Of course
other sockets cannot use the same
(address,port,peer-address,peer-port) 4-tuple as this socket, so
there is no risk of confusing the two TCP connections.
See also addressReusable().
void QSocketDevice::setBlocking ( bool enable ) [virtual]
Makes the socket blocking if enable is TRUE or nonblocking if
enable is FALSE.
Sockets are blocking by default, but we recommend using
nonblocking socket operations, especially for GUI programs that
need to be responsive.
Warning: On Windows, this function should be used with care since
whenever you use a QSocketNotifier on Windows, the socket is
immediately made nonblocking.
See also blocking() and isValid().
void QSocketDevice::setError ( Error err ) [protected]
Allows subclasses to set the error state to err.
void QSocketDevice::setReceiveBufferSize ( uint size ) [virtual]
Sets the size of the operating system receive buffer to size.
The operating system receive buffer size effectively limits two
things: how much data can be in transit at any one moment, and how
much data can be received in one iteration of the main event loop.
The default is operating system-dependent. A socket that receives
large amounts of data is probably best with a buffer size of
49152.
void QSocketDevice::setSendBufferSize ( uint size ) [virtual]
Sets the size of the operating system send buffer to size.
The operating system send buffer size effectively limits how much
data can be in transit at any one moment.
The default is operating system-dependent. A socket that sends
large amounts of data is probably best with a buffer size of
49152.
void QSocketDevice::setSocket ( int socket, Type type ) [virtual]
Sets the socket device to operate on the existing socket socket.
The type argument must match the actual socket type; use QSocketDevice::Stream for a reliable, connection-oriented TCP
socket, or QSocketDevice::Datagram for an unreliable,
connectionless UDP socket.
Any existing socket is closed.
See also isValid() and close().
int QSocketDevice::socket () const
Returns the socket number, or -1 if it is an invalid socket.
See also isValid() and type().
Type QSocketDevice::type () const
Returns the socket type which is either QSocketDevice::Stream
or QSocketDevice::Datagram.
See also socket().
Q_LONG QSocketDevice::waitForMore ( int msecs, bool * timeout = 0 ) const
Wait up to msecs milliseconds for more data to be available. If
msecs is -1 the call will block indefinitely.
Returns the number of bytes available for reading, or -1 if an
error occurred.
If timeout is non-null and no error occurred (i.e. it does not
return -1): this function sets *timeout to TRUE, if the reason
for returning was that the timeout was reached; otherwise it sets
*timeout to FALSE. This is useful to find out if the peer
closed the connection.
Warning: This is a blocking call and should be avoided in event
driven applications.
See also bytesAvailable().
Q_LONG QSocketDevice::writeBlock ( const char * data, Q_ULONG len ) [virtual]
Writes len bytes to the socket from data and returns the
number of bytes written. Returns -1 if an error occurred.
This is used for QSocketDevice::Stream sockets.
Reimplemented from QIODevice.
Q_LONG QSocketDevice::writeBlock ( const char * data, Q_ULONG len, const QHostAddress & host, Q_UINT16 port ) [virtual]
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Writes len bytes to the socket from data and returns the
number of bytes written. Returns -1 if an error occurred.
This is used for QSocketDevice::Datagram sockets. You must
specify the host and port of the destination of the data.
This file is part of the Qt toolkit.
Copyright © 1995-2003
Trolltech. All Rights Reserved.
