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Internal/Contributor docs for the Qt SDK. <b>Note:</b> These are NOT official API docs; those are found <a href='https://doc.qt.io/'>here</a>.
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Public Member Functions | Protected Member Functions | List of all members
QTcpSocket Class Reference

The QTcpSocket class provides a TCP socket. More...

#include <qtcpsocket.h>

+ Inheritance diagram for QTcpSocket:
+ Collaboration diagram for QTcpSocket:

Public Member Functions

 QTcpSocket (QObject *parent=nullptr)
 Creates a QTcpSocket object in state UnconnectedState.
 
virtual ~QTcpSocket ()
 Destroys the socket, closing the connection if necessary.
 
- Public Member Functions inherited from QAbstractSocket
 QAbstractSocket (SocketType socketType, QObject *parent)
 Creates a new abstract socket of type socketType.
 
virtual ~QAbstractSocket ()
 Destroys the socket.
 
virtual void resume ()
 
PauseModes pauseMode () const
 
void setPauseMode (PauseModes pauseMode)
 
virtual bool bind (const QHostAddress &address, quint16 port=0, BindMode mode=DefaultForPlatform)
 
bool bind (QHostAddress::SpecialAddress addr, quint16 port=0, BindMode mode=DefaultForPlatform)
 
bool bind (quint16 port=0, BindMode mode=DefaultForPlatform)
 
virtual void connectToHost (const QString &hostName, quint16 port, OpenMode mode=ReadWrite, NetworkLayerProtocol protocol=AnyIPProtocol)
 Attempts to make a connection to hostName on the given port.
 
void connectToHost (const QHostAddress &address, quint16 port, OpenMode mode=ReadWrite)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Attempts to make a connection to address on port port.
 
virtual void disconnectFromHost ()
 Attempts to close the socket.
 
bool isValid () const
 Returns true if the socket is valid and ready for use; otherwise returns false.
 
qint64 bytesAvailable () const override
 Returns the number of incoming bytes that are waiting to be read.
 
qint64 bytesToWrite () const override
 Returns the number of bytes that are waiting to be written.
 
quint16 localPort () const
 Returns the host port number (in native byte order) of the local socket if available; otherwise returns 0.
 
QHostAddress localAddress () const
 Returns the host address of the local socket if available; otherwise returns QHostAddress::Null.
 
quint16 peerPort () const
 Returns the port of the connected peer if the socket is in ConnectedState; otherwise returns 0.
 
QHostAddress peerAddress () const
 Returns the address of the connected peer if the socket is in ConnectedState; otherwise returns QHostAddress::Null.
 
QString peerName () const
 Returns the name of the peer as specified by connectToHost(), or an empty QString if connectToHost() has not been called.
 
qint64 readBufferSize () const
 Returns the size of the internal read buffer.
 
virtual void setReadBufferSize (qint64 size)
 Sets the size of QAbstractSocket's internal read buffer to be size bytes.
 
void abort ()
 Aborts the current connection and resets the socket.
 
virtual qintptr socketDescriptor () const
 Returns the native socket descriptor of the QAbstractSocket object if this is available; otherwise returns -1.
 
virtual bool setSocketDescriptor (qintptr socketDescriptor, SocketState state=ConnectedState, OpenMode openMode=ReadWrite)
 Initializes QAbstractSocket with the native socket descriptor socketDescriptor.
 
virtual void setSocketOption (QAbstractSocket::SocketOption option, const QVariant &value)
 
virtual QVariant socketOption (QAbstractSocket::SocketOption option)
 
SocketType socketType () const
 Returns the socket type (TCP, UDP, or other).
 
SocketState state () const
 Returns the state of the socket.
 
SocketError error () const
 Returns the type of error that last occurred.
 
void close () override
 Closes the I/O device for the socket and calls disconnectFromHost() to close the socket's connection.
 
bool isSequential () const override
 \reimp
 
bool flush ()
 This function writes as much as possible from the internal write buffer to the underlying network socket, without blocking.
 
virtual bool waitForConnected (int msecs=30000)
 Waits until the socket is connected, up to msecs milliseconds.
 
bool waitForReadyRead (int msecs=30000) override
 This function blocks until new data is available for reading and the \l{QIODevice::}{readyRead()} signal has been emitted.
 
bool waitForBytesWritten (int msecs=30000) override
 \reimp
 
virtual bool waitForDisconnected (int msecs=30000)
 Waits until the socket has disconnected, up to msecs milliseconds.
 
void setProxy (const QNetworkProxy &networkProxy)
 
QNetworkProxy proxy () const
 
QString protocolTag () const
 
void setProtocolTag (const QString &tag)
 
- Public Member Functions inherited from QIODevice
 QIODevice ()
 Constructs a QIODevice object.
 
 QIODevice (QObject *parent)
 Constructs a QIODevice object with the given parent.
 
virtual ~QIODevice ()
 The destructor is virtual, and QIODevice is an abstract base class.
 
QIODeviceBase::OpenMode openMode () const
 Returns the mode in which the device has been opened; i.e.
 
void setTextModeEnabled (bool enabled)
 If enabled is true, this function sets the \l Text flag on the device; otherwise the \l Text flag is removed.
 
bool isTextModeEnabled () const
 Returns true if the \l Text flag is enabled; otherwise returns false.
 
bool isOpen () const
 Returns true if the device is open; otherwise returns false.
 
bool isReadable () const
 Returns true if data can be read from the device; otherwise returns false.
 
bool isWritable () const
 Returns true if data can be written to the device; otherwise returns false.
 
int readChannelCount () const
 
int writeChannelCount () const
 
int currentReadChannel () const
 
void setCurrentReadChannel (int channel)
 
int currentWriteChannel () const
 
void setCurrentWriteChannel (int channel)
 
virtual bool open (QIODeviceBase::OpenMode mode)
 Opens the device and sets its OpenMode to mode.
 
virtual qint64 pos () const
 For random-access devices, this function returns the position that data is written to or read from.
 
virtual qint64 size () const
 For open random-access devices, this function returns the size of the device.
 
virtual bool seek (qint64 pos)
 For random-access devices, this function sets the current position to pos, returning true on success, or false if an error occurred.
 
virtual bool atEnd () const
 Returns true if the current read and write position is at the end of the device (i.e.
 
virtual bool reset ()
 Seeks to the start of input for random-access devices.
 
qint64 read (char *data, qint64 maxlen)
 Reads at most maxSize bytes from the device into data, and returns the number of bytes read.
 
QByteArray read (qint64 maxlen)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads at most maxSize bytes from the device, and returns the data read as a QByteArray.
 
QByteArray readAll ()
 Reads all remaining data from the device, and returns it as a byte array.
 
qint64 readLine (char *data, qint64 maxlen)
 This function reads a line of ASCII characters from the device, up to a maximum of maxSize - 1 bytes, stores the characters in data, and returns the number of bytes read.
 
QByteArray readLine (qint64 maxlen=0)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a line from the device, but no more than maxSize characters, and returns the result as a byte array.
 
virtual bool canReadLine () const
 Returns true if a complete line of data can be read from the device; otherwise returns false.
 
void startTransaction ()
 
void commitTransaction ()
 
void rollbackTransaction ()
 
bool isTransactionStarted () const
 
qint64 write (const char *data, qint64 len)
 Writes at most maxSize bytes of data from data to the device.
 
qint64 write (const char *data)
 
qint64 write (const QByteArray &data)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes the content of data to the device.
 
qint64 peek (char *data, qint64 maxlen)
 
QByteArray peek (qint64 maxlen)
 
qint64 skip (qint64 maxSize)
 
void ungetChar (char c)
 Puts the character c back into the device, and decrements the current position unless the position is 0.
 
bool putChar (char c)
 Writes the character c to the device.
 
bool getChar (char *c)
 Reads one character from the device and stores it in c.
 
QString errorString () const
 Returns a human-readable description of the last device error that occurred.
 
- Public Member Functions inherited from QObject
Q_INVOKABLE QObject (QObject *parent=nullptr)
 Constructs an object with parent object parent.
 
virtual ~QObject ()
 Destroys the object, deleting all its child objects.
 
virtual bool event (QEvent *event)
 This virtual function receives events to an object and should return true if the event e was recognized and processed.
 
virtual bool eventFilter (QObject *watched, QEvent *event)
 Filters events if this object has been installed as an event filter for the watched object.
 
QString objectName () const
 
Q_WEAK_OVERLOAD void setObjectName (const QString &name)
 Sets the object's name to name.
 
void setObjectName (QAnyStringView name)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
 
QBindable< QString > bindableObjectName ()
 
bool isWidgetType () const
 Returns true if the object is a widget; otherwise returns false.
 
bool isWindowType () const
 Returns true if the object is a window; otherwise returns false.
 
bool isQuickItemType () const
 Returns true if the object is a QQuickItem; otherwise returns false.
 
bool signalsBlocked () const noexcept
 Returns true if signals are blocked; otherwise returns false.
 
bool blockSignals (bool b) noexcept
 If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it).
 
QThread * thread () const
 Returns the thread in which the object lives.
 
bool moveToThread (QThread *thread QT6_DECL_NEW_OVERLOAD_TAIL)
 Changes the thread affinity for this object and its children and returns true on success.
 
int startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
 This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.
 
int startTimer (std::chrono::nanoseconds time, Qt::TimerType timerType=Qt::CoarseTimer)
 
void killTimer (int id)
 Kills the timer with timer identifier, id.
 
void killTimer (Qt::TimerId id)
 
template<typename T >
T findChild (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.
 
template<typename T >
QList< T > findChildren (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects.
 
template<typename T >
T findChild (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
 
template<typename T >
QList< T > findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
 
const QObjectList & children () const
 Returns a list of child objects.
 
void setParent (QObject *parent)
 Makes the object a child of parent.
 
void installEventFilter (QObject *filterObj)
 Installs an event filter filterObj on this object.
 
void removeEventFilter (QObject *obj)
 Removes an event filter object obj from this object.
 
QMetaObject::Connection connect (const QObject *sender, const char *signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const
 
bool disconnect (const char *signal=nullptr, const QObject *receiver=nullptr, const char *member=nullptr) const
 
bool disconnect (const QObject *receiver, const char *member=nullptr) const
 
void dumpObjectTree () const
 Dumps a tree of children to the debug output.
 
void dumpObjectInfo () const
 Dumps information about signal connections, etc.
 
bool setProperty (const char *name, const QVariant &value)
 Sets the value of the object's name property to value.
 
bool setProperty (const char *name, QVariant &&value)
 
QVariant property (const char *name) const
 Returns the value of the object's name property.
 
QList< QByteArray > dynamicPropertyNames () const
 
QBindingStorage * bindingStorage ()
 
const QBindingStorage * bindingStorage () const
 
QObject * parent () const
 Returns a pointer to the parent object.
 
bool inherits (const char *classname) const
 Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false.
 

Protected Member Functions

 QTcpSocket (QTcpSocketPrivate &dd, QObject *parent=nullptr)
 
 QTcpSocket (QAbstractSocket::SocketType socketType, QTcpSocketPrivate &dd, QObject *parent=nullptr)
 
- Protected Member Functions inherited from QAbstractSocket
qint64 readData (char *data, qint64 maxlen) override
 \reimp
 
qint64 readLineData (char *data, qint64 maxlen) override
 \reimp
 
qint64 skipData (qint64 maxSize) override
 \reimp
 
qint64 writeData (const char *data, qint64 len) override
 \reimp
 
void setSocketState (SocketState state)
 Sets the state of the socket to state.
 
void setSocketError (SocketError socketError)
 Sets the type of error that last occurred to socketError.
 
void setLocalPort (quint16 port)
 
void setLocalAddress (const QHostAddress &address)
 
void setPeerPort (quint16 port)
 
void setPeerAddress (const QHostAddress &address)
 
void setPeerName (const QString &name)
 
 QAbstractSocket (SocketType socketType, QAbstractSocketPrivate &dd, QObject *parent=nullptr)
 
- Protected Member Functions inherited from QIODevice
 QIODevice (QIODevicePrivate &dd, QObject *parent=nullptr)
 
void setOpenMode (QIODeviceBase::OpenMode openMode)
 Sets the OpenMode of the device to openMode.
 
void setErrorString (const QString &errorString)
 Sets the human readable description of the last device error that occurred to str.
 
- Protected Member Functions inherited from QObject
QObject * sender () const
 Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns \nullptr.
 
int senderSignalIndex () const
 
int receivers (const char *signal) const
 Returns the number of receivers connected to the signal.
 
bool isSignalConnected (const QMetaMethod &signal) const
 
virtual void timerEvent (QTimerEvent *event)
 This event handler can be reimplemented in a subclass to receive timer events for the object.
 
virtual void childEvent (QChildEvent *event)
 This event handler can be reimplemented in a subclass to receive child events.
 
virtual void customEvent (QEvent *event)
 This event handler can be reimplemented in a subclass to receive custom events.
 
virtual void connectNotify (const QMetaMethod &signal)
 
virtual void disconnectNotify (const QMetaMethod &signal)
 
 QObject (QObjectPrivate &dd, QObject *parent=nullptr)
 
- Protected Member Functions inherited from QIODeviceBase
 ~QIODeviceBase ()=default
 

Additional Inherited Members

- Public Types inherited from QAbstractSocket
enum  SocketType { TcpSocket , UdpSocket , SctpSocket , UnknownSocketType = -1 }
 This enum describes the transport layer protocol. More...
 
enum  SocketError {
  ConnectionRefusedError , RemoteHostClosedError , HostNotFoundError , SocketAccessError ,
  SocketResourceError , SocketTimeoutError , DatagramTooLargeError , NetworkError ,
  AddressInUseError , SocketAddressNotAvailableError , UnsupportedSocketOperationError , UnfinishedSocketOperationError ,
  ProxyAuthenticationRequiredError , SslHandshakeFailedError , ProxyConnectionRefusedError , ProxyConnectionClosedError ,
  ProxyConnectionTimeoutError , ProxyNotFoundError , ProxyProtocolError , OperationError ,
  SslInternalError , SslInvalidUserDataError , TemporaryError , UnknownSocketError = -1
}
 This enum describes the socket errors that can occur. More...
 
enum  SocketState {
  UnconnectedState , HostLookupState , ConnectingState , ConnectedState ,
  BoundState , ListeningState , ClosingState
}
 This enum describes the different states in which a socket can be. More...
 
enum  SocketOption {
  LowDelayOption , KeepAliveOption , MulticastTtlOption , MulticastLoopbackOption ,
  TypeOfServiceOption , SendBufferSizeSocketOption , ReceiveBufferSizeSocketOption , PathMtuSocketOption
}
 
enum  BindFlag { DefaultForPlatform = 0x0 , ShareAddress = 0x1 , DontShareAddress = 0x2 , ReuseAddressHint = 0x4 }
 
enum  PauseMode { PauseNever = 0x0 , PauseOnSslErrors = 0x1 }
 
using NetworkLayerProtocol = QHostAddress::NetworkLayerProtocol
 
- Public Types inherited from QIODeviceBase
enum  OpenModeFlag {
  NotOpen = 0x0000 , ReadOnly = 0x0001 , WriteOnly = 0x0002 , ReadWrite = ReadOnly | WriteOnly ,
  Append = 0x0004 , Truncate = 0x0008 , Text = 0x0010 , Unbuffered = 0x0020 ,
  NewOnly = 0x0040 , ExistingOnly = 0x0080
}
 This enum is used with QIODevice::open() to describe the mode in which a device is opened. More...
 
- Public Slots inherited from QObject
void deleteLater ()
 \threadsafe
 
- Signals inherited from QAbstractSocket
void hostFound ()
 This signal is emitted after connectToHost() has been called and the host lookup has succeeded.
 
void connected ()
 This signal is emitted after connectToHost() has been called and a connection has been successfully established.
 
void disconnected ()
 This signal is emitted when the socket has been disconnected.
 
void stateChanged (QAbstractSocket::SocketState)
 This signal is emitted whenever QAbstractSocket's state changes.
 
void errorOccurred (QAbstractSocket::SocketError)
 
void proxyAuthenticationRequired (const QNetworkProxy &proxy, QAuthenticator *authenticator)
 
- Signals inherited from QIODevice
void readyRead ()
 This signal is emitted once every time new data is available for reading from the device's current read channel.
 
void channelReadyRead (int channel)
 
void bytesWritten (qint64 bytes)
 This signal is emitted every time a payload of data has been written to the device's current write channel.
 
void channelBytesWritten (int channel, qint64 bytes)
 
void aboutToClose ()
 This signal is emitted when the device is about to close.
 
void readChannelFinished ()
 
- Signals inherited from QObject
void destroyed (QObject *=nullptr)
 This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.
 
void objectNameChanged (const QString &objectName, QPrivateSignal)
 This signal is emitted after the object's name has been changed.
 
- Static Public Member Functions inherited from QObject
static QMetaObject::Connection connect (const QObject *sender, const char *signal, const QObject *receiver, const char *member, Qt::ConnectionType=Qt::AutoConnection)
 \threadsafe
 
static QMetaObject::Connection connect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)
 
template<typename Func1 , typename Func2 >
static QMetaObject::Connection connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType *context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)
 
template<typename Func1 , typename Func2 >
static QMetaObject::Connection connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)
 
static bool disconnect (const QObject *sender, const char *signal, const QObject *receiver, const char *member)
 \threadsafe
 
static bool disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &member)
 
static bool disconnect (const QMetaObject::Connection &)
 Disconnect a connection.
 
template<typename Func1 , typename Func2 >
static bool disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object *receiver, Func2 slot)
 
template<typename Func1 >
static bool disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, const QObject *receiver, void **zero)
 
- Static Public Attributes inherited from QAbstractSocket
static constexpr auto IPv4Protocol = QHostAddress::IPv4Protocol
 
static constexpr auto IPv6Protocol = QHostAddress::IPv6Protocol
 
static constexpr auto AnyIPProtocol = QHostAddress::AnyIPProtocol
 
static constexpr auto UnknownNetworkLayerProtocol = QHostAddress::UnknownNetworkLayerProtocol
 
- Protected Attributes inherited from QObject
QScopedPointer< QObjectData > d_ptr
 
- Properties inherited from QObject
QString objectName
 the name of this object
 
- Related Symbols inherited from QObject
 Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.
 
 
 
 \macro Q_CLASSINFO(Name, Value)
 

Detailed Description

The QTcpSocket class provides a TCP socket.

\reentrant

\inmodule QtNetwork

TCP (Transmission Control Protocol) is a reliable, stream-oriented, connection-oriented transport protocol. It is especially well suited for continuous transmission of data.

QTcpSocket is a convenience subclass of QAbstractSocket that allows you to establish a TCP connection and transfer streams of data. See the QAbstractSocket documentation for details.

Note
TCP sockets cannot be opened in QIODevice::Unbuffered mode.
See also
QTcpServer, QUdpSocket, QNetworkAccessManager, {Fortune Server}, {Fortune Client}, {Threaded Fortune Server}, {Blocking Fortune Client}, {Torrent Example}

Definition at line 17 of file qtcpsocket.h.

Constructor & Destructor Documentation

◆ QTcpSocket() [1/3]

QT_BEGIN_NAMESPACE QTcpSocket::QTcpSocket ( QObject * parent = nullptr)
explicit

Creates a QTcpSocket object in state UnconnectedState.

parent is passed on to the QObject constructor.

See also
socketType()

Definition at line 45 of file qtcpsocket.cpp.

References qDebug.

◆ ~QTcpSocket()

QTcpSocket::~QTcpSocket ( )
virtual

Destroys the socket, closing the connection if necessary.

See also
close()

Definition at line 60 of file qtcpsocket.cpp.

References qDebug.

◆ QTcpSocket() [2/3]

QTcpSocket::QTcpSocket ( QTcpSocketPrivate & dd,
QObject * parent = nullptr )
protected

Definition at line 70 of file qtcpsocket.cpp.

◆ QTcpSocket() [3/3]

QTcpSocket::QTcpSocket ( QAbstractSocket::SocketType socketType,
QTcpSocketPrivate & dd,
QObject * parent = nullptr )
protected

Definition at line 79 of file qtcpsocket.cpp.

The documentation for this class was generated from the following files: