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# TQSocketDevice Class Reference
[network module]

The TQSocketDevice class provides a platform-independent low-level socket API. More...

`#include <ntqsocketdevice.h>`

Inherits TQIODevice.

List of all member functions.

## Public Members

- enum Type { Stream, Datagram }
- enum Protocol { IPv4, IPv6, Unknown }
- TQSocketDevice ( Type type = Stream )
- TQSocketDevice ( Type type, Protocol protocol, int dummy )
- TQSocketDevice ( int socket, Type type )
- virtual ~TQSocketDevice ()
- bool isValid () const
- Type type () const
- Protocol protocol () const
- int socket () const
- virtual void setSocket ( int socket, Type type )
- bool blocking () const
- virtual void setBlocking ( bool enable )
- bool addressReusable () const
- virtual void setAddressReusable ( bool enable )
- int receiveBufferSize () const
- virtual void setReceiveBufferSize ( uint size )
- int sendBufferSize () const
- virtual void setSendBufferSize ( uint size )
- virtual bool connect ( const TQHostAddress & addr, TQ_UINT16 port )
- virtual bool bind ( const TQHostAddress & address, TQ_UINT16 port )
- virtual bool listen ( int backlog )
- virtual int accept ()
- TQ_LONG bytesAvailable () const
- TQ_LONG waitForMore ( int msecs, bool * timeout = 0 ) const
- virtual TQ_LONG readBlock ( char * data, TQ_ULONG maxlen )
- virtual TQ_LONG writeBlock ( const char * data, TQ_ULONG len )
- virtual TQ_LONG writeBlock ( const char * data, TQ_ULONG len, const TQHostAddress & host, TQ_UINT16 port )
- TQ_UINT16 port () const
- TQ_UINT16 peerPort () const
- TQHostAddress address () const
- TQHostAddress peerAddress () const
- enum Error { NoError, AlreadyBound, Inaccessible, NoResources, InternalError, Bug = InternalError, Impossible, NoFiles, ConnectionRefused, NetworkFailure, UnknownError }
- Error error () const

## Protected Members

- void setError ( Error err )

## Detailed Description

The TQSocketDevice 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 TQSocket class provides a much easier and high level alternative, but certain things (like UDP) can't be done with TQSocket and if you need a platform-independent API for those, TQSocketDevice is the right choice.

The essential purpose of the class is to provide a TQIODevice that works on sockets, wrapped in a platform-independent API.

When calling connect() or bind(), TQSocketDevice detects the protocol family (IPv4, IPv6) automatically. Passing the protocol family to TQSocketDevice'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 TQSocket, TQSocketNotifier, TQHostAddress, and Input/Output and Networking.

## Member Type Documentation

### TQSocketDevice::Error

This enum type describes the error states of TQSocketDevice.

- `TQSocketDevice::NoError` - No error has occurred.
- `TQSocketDevice::AlreadyBound` - The device is already bound, according to bind().
- `TQSocketDevice::Inaccessible` - The operating system or firewall prohibited the action.
- `TQSocketDevice::NoResources` - The operating system ran out of a resource.
- `TQSocketDevice::InternalError` - An internal error occurred in TQSocketDevice.
- `TQSocketDevice::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 TQSocketDevice is not aware of this. So when you call writeBlock(), the impossible happens.
- `TQSocketDevice::NoFiles` - The operating system will not let TQSocketDevice open another file.
- `TQSocketDevice::ConnectionRefused` - A connection attempt was rejected by the peer.
- `TQSocketDevice::NetworkFailure` - There is a network failure.
- `TQSocketDevice::UnknownError` - The operating system did something unexpected.

### TQSocketDevice::Protocol

This enum type describes the protocol family of the socket. Possible values are:

- `TQSocketDevice::IPv4` - The socket is an IPv4 socket.
- `TQSocketDevice::IPv6` - The socket is an IPv6 socket.
- `TQSocketDevice::Unknown` - The protocol family of the socket is not known. This can happen if you use TQSocketDevice with an already existing socket; it tries to determine the protocol family, but this can fail if the protocol family is not known to TQSocketDevice.

See also protocol() and setSocket().

### TQSocketDevice::Type

This enum type describes the type of the socket:

- `TQSocketDevice::Stream` - a stream socket (TCP, usually)
- `TQSocketDevice::Datagram` - a datagram socket (UDP, usually)

## Member Function Documentation

### TQSocketDevice::TQSocketDevice ( Type type = Stream )

Creates a TQSocketDevice object for a stream or datagram socket.

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

The socket is created as an IPv4 socket.

See also blocking() and protocol().

### TQSocketDevice::TQSocketDevice ( Type type, Protocol protocol, int dummy )

Creates a TQSocketDevice object for a stream or datagram socket.

The type argument must be either TQSocketDevice::Stream for a reliable, connection-oriented TCP socket, or TQSocketDevice::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().

### TQSocketDevice::TQSocketDevice ( int socket, Type type )

Creates a TQSocketDevice object for the existing socket socket.

The type argument must match the actual socket type; use TQSocketDevice::Stream for a reliable, connection-oriented TCP socket, or TQSocketDevice::Datagram for an unreliable, connectionless UDP socket.

### TQSocketDevice::~TQSocketDevice ()`[virtual]`

Destroys the socket device and closes the socket if it is open.

### int TQSocketDevice::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().

### TQHostAddress TQSocketDevice::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 TQSocketDevice::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 TQSocketDevice::bind ( const TQHostAddress & address, TQ_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 TQSocketDevice::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().

### TQ_LONG TQSocketDevice::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(). TQSocket has workarounds to deal with this problem.

### bool TQSocketDevice::connect ( const TQHostAddress & addr, TQ_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 TQSocketDevice::error () const

Returns the first error seen.

### bool TQSocketDevice::isValid () const

Returns TRUE if this is a valid socket; otherwise returns FALSE.

See also socket().

### bool TQSocketDevice::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().

### TQHostAddress TQSocketDevice::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.

### TQ_UINT16 TQSocketDevice::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.

### TQ_UINT16 TQSocketDevice::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 TQt always uses native byte order, i.e. 67 is 67 in TQt; there is no need to call htons().

### Protocol TQSocketDevice::protocol () const

Returns the socket's protocol family, which is one of Unknown, IPv4, or IPv6.

TQSocketDevice 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().

### TQ_LONG TQSocketDevice::readBlock ( char * data, TQ_ULONG maxlen )`[virtual]`

Reads maxlen bytes from the socket into data and returns the number of bytes read. Returns -1 if an error occurred. Returning 0 is not an error. For Stream sockets, 0 is returned when the remote host closes the connection. For Datagram sockets, 0 is a valid datagram size.

Reimplemented from TQIODevice.

### int TQSocketDevice::receiveBufferSize () const

Returns the size of the operating system receive buffer.

See also setReceiveBufferSize().

### int TQSocketDevice::sendBufferSize () const

Returns the size of the operating system send buffer.

See also setSendBufferSize().

### void TQSocketDevice::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 TQSocketDevice::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 TQSocketNotifier on Windows, the socket is immediately made nonblocking.

See also blocking() and isValid().

### void TQSocketDevice::setError ( Error err )`[protected]`

Allows subclasses to set the error state to err.

### void TQSocketDevice::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 TQSocketDevice::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 TQSocketDevice::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 TQSocketDevice::Stream for a reliable, connection-oriented TCP socket, or TQSocketDevice::Datagram for an unreliable, connectionless UDP socket.

Any existing socket is closed.

See also isValid() and close().

### int TQSocketDevice::socket () const

Returns the socket number, or -1 if it is an invalid socket.

See also isValid() and type().

### Type TQSocketDevice::type () const

Returns the socket type which is either TQSocketDevice::Stream or TQSocketDevice::Datagram.

See also socket().

### TQ_LONG TQSocketDevice::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().

### TQ_LONG TQSocketDevice::writeBlock ( const char * data, TQ_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 TQSocketDevice::Stream sockets.

Reimplemented from TQIODevice.

### TQ_LONG TQSocketDevice::writeBlock ( const char * data, TQ_ULONG len, const TQHostAddress & host, TQ_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 TQSocketDevice::Datagram sockets. You must specify the host and port of the destination of the data.

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