QSocketDevice

NAME

SYNOPSIS

Inherits QIODevice.

Public Members

Protected Members

DESCRIPTION

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 things (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.

When calling connect() or bind(), QSocketDevice detects the protocol family (IPv4, IPv6) automatically. Passing the protocol family to QSocketDevice's constructor or to setSocket() forces creation of a socket device of a specific protocol. If not set, the protocol will be detected at the first call to connect() or bind().

See also QSocket, QSocketNotifier, QHostAddress, and Input/Output and Networking.  

Member Type Documentation

QSocketDevice::Error

QSocketDevice::NoError - No error has occurred.

QSocketDevice::AlreadyBound - The device is already bound, according to bind().

QSocketDevice::Inaccessible - The operating system or firewall prohibited the action.

QSocketDevice::NoResources - The operating system ran out of a resource.

QSocketDevice::InternalError - An internal error occurred in QSocketDevice.

QSocketDevice::Impossible - An attempt was made to do something which makes no sense. For example:

    ::close( sd->socket() );


    sd->writeBlock( someData, 42 );

The libc ::close() closes the socket, but QSocketDevice is not aware of this. So when you call writeBlock(), the impossible happens.

QSocketDevice::NoFiles - The operating system will not let QSocketDevice open another file.

QSocketDevice::ConnectionRefused - A connection attempt was rejected by the peer.

QSocketDevice::NetworkFailure - There is a network failure.

QSocketDevice::UnknownError - The operating system did something unexpected.

QSocketDevice::Protocol

QSocketDevice::IPv4 - The socket is an IPv4 socket.

QSocketDevice::IPv6 - The socket is an IPv6 socket.

QSocketDevice::Unknown - The protocol family of the socket is not known. This can happen if you use QSocketDevice with an already existing socket; it tries to determine the protocol family, but this can fail if the protocol family is not known to QSocketDevice.

See also protocol() and setSocket().  

QSocketDevice::Type

QSocketDevice::Stream - a stream socket (TCP, usually)

QSocketDevice::Datagram - a datagram socket (UDP, usually)

MEMBER FUNCTION DOCUMENTATION

QSocketDevice::QSocketDevice ( Type type = Stream )

The type argument must be either QSocketDevice::Stream for a reliable, connection-oriented TCP socket, or QSocketDevice::Datagram for an unreliable UDP socket.

The socket is created as an IPv4 socket.

See also blocking() and protocol().  

QSocketDevice::QSocketDevice ( Type type, Protocol protocol, int dummy )

The type argument must be either QSocketDevice::Stream for a reliable, connection-oriented TCP socket, or QSocketDevice::Datagram for an unreliable UDP socket.

The protocol indicates whether the socket should be of type IPv4 or IPv6. Passing Unknown is not meaningful in this context and you should avoid using (it creates an IPv4 socket, but your code is not easily readable).

The argument dummy is necessary for compatibility with some compilers.

See also blocking() and protocol().  

QSocketDevice::QSocketDevice ( int socket, Type type )

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]

int QSocketDevice::accept () [virtual]

See also bind() and listen().  

QHostAddress QSocketDevice::address () const

bool QSocketDevice::addressReusable () const

See also setAddressReusable().  

bool QSocketDevice::bind ( const QHostAddress & address, Q_UINT16 port ) [virtual]

bind() is used by servers for setting up incoming connections. Call bind() before listen().  

bool QSocketDevice::blocking () const

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

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]

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

bool QSocketDevice::isValid () const

See also socket().  

bool QSocketDevice::listen ( int backlog ) [virtual]

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

Note that for Datagram sockets, this is the source port of the last packet received.  

Q_UINT16 QSocketDevice::peerPort () const

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

Note that Qt always uses native byte order, i.e. 67 is 67 in Qt; there is no need to call htons().  

Protocol QSocketDevice::protocol () const

QSocketDevice either creates a socket with a well known protocol family or it uses an already existing socket. In the first case, this function returns the protocol family it was constructed with. In the second case, it tries to determine the protocol family of the socket; if this fails, it returns Unknown.

See also Protocol and setSocket().  

Q_LONG QSocketDevice::readBlock ( char * data, Q_ULONG maxlen ) [virtual]

Reimplemented from QIODevice.  

int QSocketDevice::receiveBufferSize () const

See also setReceiveBufferSize().  

int QSocketDevice::sendBufferSize () const

See also setSendBufferSize().  

void QSocketDevice::setAddressReusable ( bool enable ) [virtual]

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]

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]

void QSocketDevice::setReceiveBufferSize ( uint size ) [virtual]

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]

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]

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

See also isValid() and type().  

Type QSocketDevice::type () const

See also socket().  

Q_LONG QSocketDevice::waitForMore ( int msecs, bool * timeout = 0 ) const

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]

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]

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.

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