QSslSocket Class

 QSslSocket *socket = new QSslSocket(this);
 connect(socket, &QSslSocket::encrypted, this, &Receiver::ready);

 socket->connectToHostEncrypted("imap.example.com", 993);

 void SslServer::incomingConnection(qintptr socketDescriptor)
 {
     QSslSocket *serverSocket = new QSslSocket;
     if (serverSocket->setSocketDescriptor(socketDescriptor)) {
         addPendingConnection(serverSocket);
         connect(serverSocket, &QSslSocket::encrypted, this, &SslServer::ready);
         serverSocket->startServerEncryption();
     } else {
         delete serverSocket;
     }
 }

 QSslSocket socket;
 socket.connectToHostEncrypted("http.example.com", 443);
 if (!socket.waitForEncrypted()) {
     qDebug() << socket.errorString();
     return false;
 }

 socket.write("GET / HTTP/1.0\r\n\r\n");
 while (socket.waitForReadyRead())
     qDebug() << socket.readAll().data();

 QList<QSslCertificate> certificates = getCertificates();
 QSslConfiguration configuration = QSslConfiguration::defaultConfiguration();
 configuration.addCaCertificates(certificates);
 QSslConfiguration::setDefaultConfiguration(configuration);

Member Function Documentation

[explicit] QSslSocket::QSslSocket(QObject *parent = nullptr)

Constructs a QSslSocket object. parent is passed to QObject's constructor. The new socket's cipher suite is set to the one returned by the static method defaultCiphers().

[virtual noexcept] QSslSocket::~QSslSocket()

Destroys the QSslSocket.

[static, since 6.1] QString QSslSocket::activeBackend()

Returns the name of the backend that QSslSocket and related classes use. If the active backend was not set explicitly, this function returns the name of a default backend that QSslSocket selects implicitly from the list of available backends.

This function was introduced in Qt 6.1.

See also setActiveBackend() and availableBackends().

[signal] void QSslSocket::alertReceived(QSsl::AlertLevel level, QSsl::AlertType type, const QString &description)

QSslSocket emits this signal if an alert message was received from a peer. level tells if the alert was fatal or it was a warning. type is the code explaining why the alert was sent. When a textual description of the alert message is available, it is supplied in description.

See also alertSent(), QSsl::AlertLevel, and QSsl::AlertType.

[signal] void QSslSocket::alertSent(QSsl::AlertLevel level, QSsl::AlertType type, const QString &description)

QSslSocket emits this signal if an alert message was sent to a peer. level describes if it was a warning or a fatal error. type gives the code of the alert message. When a textual description of the alert message is available, it is supplied in description.

See also alertReceived(), QSsl::AlertLevel, and QSsl::AlertType.

[override virtual] bool QSslSocket::atEnd() const

Reimplements: QIODevice::atEnd() const.

[static, since 6.1] QList<QString> QSslSocket::availableBackends()

Returns the names of the currently available backends. These names are in lower case, e.g. "openssl", "securetransport", "schannel" (similar to the already existing feature names for TLS backends in Qt).

This function was introduced in Qt 6.1.

See also activeBackend().

[override virtual] qint64 QSslSocket::bytesAvailable() const

Reimplements: QAbstractSocket::bytesAvailable() const.

Returns the number of decrypted bytes that are immediately available for reading.

[override virtual] qint64 QSslSocket::bytesToWrite() const

Reimplements: QAbstractSocket::bytesToWrite() const.

Returns the number of unencrypted bytes that are waiting to be encrypted and written to the network.

[override virtual] bool QSslSocket::canReadLine() const

Reimplements: QIODevice::canReadLine() const.

Returns true if you can read one while line (terminated by a single ASCII '\n' character) of decrypted characters; otherwise, false is returned.

[override virtual] void QSslSocket::close()

Reimplements: QAbstractSocket::close().

void QSslSocket::connectToHostEncrypted(const QString &hostName, quint16 port, QIODeviceBase::OpenMode mode = ReadWrite, QAbstractSocket::NetworkLayerProtocol protocol = AnyIPProtocol)

Starts an encrypted connection to the device hostName on port, using mode as the OpenMode. This is equivalent to calling connectToHost() to establish the connection, followed by a call to startClientEncryption(). The protocol parameter can be used to specify which network protocol to use (eg. IPv4 or IPv6).

QSslSocket first enters the HostLookupState. Then, after entering either the event loop or one of the waitFor...() functions, it enters the ConnectingState, emits connected(), and then initiates the SSL client handshake. At each state change, QSslSocket emits signal stateChanged().

After initiating the SSL client handshake, if the identity of the peer can't be established, signal sslErrors() is emitted. If you want to ignore the errors and continue connecting, you must call ignoreSslErrors(), either from inside a slot function connected to the sslErrors() signal, or prior to entering encrypted mode. If ignoreSslErrors() is not called, the connection is dropped, signal disconnected() is emitted, and QSslSocket returns to the UnconnectedState.

If the SSL handshake is successful, QSslSocket emits encrypted().

 QSslSocket socket;
 connect(&socket, &QSslSocket::encrypted, receiver, &Receiver::socketEncrypted);

 socket.connectToHostEncrypted("imap", 993);
 socket->write("1 CAPABILITY\r\n");

The default for mode is ReadWrite.

If you want to create a QSslSocket on the server side of a connection, you should instead call startServerEncryption() upon receiving the incoming connection through QTcpServer.

See also connectToHost(), startClientEncryption(), waitForConnected(), and waitForEncrypted().

void QSslSocket::connectToHostEncrypted(const QString &hostName, quint16 port, const QString &sslPeerName, QIODeviceBase::OpenMode mode = ReadWrite, QAbstractSocket::NetworkLayerProtocol protocol = AnyIPProtocol)

This is an overloaded function.

In addition to the original behaviour of connectToHostEncrypted, this overloaded method enables the usage of a different hostname (sslPeerName) for the certificate validation instead of the one used for the TCP connection (hostName).

See also connectToHostEncrypted().

[since 6.0] void QSslSocket::continueInterruptedHandshake()

If an application wants to conclude a handshake even after receiving handshakeInterruptedOnError() signal, it must call this function. This call must be done from a slot function attached to the signal. The signal-slot connection must be direct.

This function was introduced in Qt 6.0.

See also handshakeInterruptedOnError() and QSslConfiguration::setHandshakeMustInterruptOnError().

[signal] void QSslSocket::encrypted()

This signal is emitted when QSslSocket enters encrypted mode. After this signal has been emitted, QSslSocket::isEncrypted() will return true, and all further transmissions on the socket will be encrypted.

See also QSslSocket::connectToHostEncrypted() and QSslSocket::isEncrypted().

qint64 QSslSocket::encryptedBytesAvailable() const

Returns the number of encrypted bytes that are awaiting decryption. Normally, this function will return 0 because QSslSocket decrypts its incoming data as soon as it can.

qint64 QSslSocket::encryptedBytesToWrite() const

Returns the number of encrypted bytes that are waiting to be written to the network.

[signal] void QSslSocket::encryptedBytesWritten(qint64 written)

This signal is emitted when QSslSocket writes its encrypted data to the network. The written parameter contains the number of bytes that were successfully written.

See also QIODevice::bytesWritten().

[signal] void QSslSocket::handshakeInterruptedOnError(const QSslError &error)

QSslSocket emits this signal if a certificate verification error was found and if early error reporting was enabled in QSslConfiguration. An application is expected to inspect the error and decide if it wants to continue the handshake, or abort it and send an alert message to the peer. The signal-slot connection must be direct.

See also continueInterruptedHandshake(), sslErrors(), and QSslConfiguration::setHandshakeMustInterruptOnError().

[slot] void QSslSocket::ignoreSslErrors()

This slot tells QSslSocket to ignore errors during QSslSocket's handshake phase and continue connecting. If you want to continue with the connection even if errors occur during the handshake phase, then you must call this slot, either from a slot connected to sslErrors(), or before the handshake phase. If you don't call this slot, either in response to errors or before the handshake, the connection will be dropped after the sslErrors() signal has been emitted.

If there are no errors during the SSL handshake phase (i.e., the identity of the peer is established with no problems), QSslSocket will not emit the sslErrors() signal, and it is unnecessary to call this function.

See also sslErrors().

void QSslSocket::ignoreSslErrors(const QList<QSslError> &errors)

This is an overloaded function.

This method tells QSslSocket to ignore only the errors given in errors.

 QList<QSslCertificate> cert = QSslCertificate::fromPath("server-certificate.pem"_L1);
 QSslError error(QSslError::SelfSignedCertificate, cert.at(0));
 QList<QSslError> expectedSslErrors;
 expectedSslErrors.append(error);

 QSslSocket socket;
 socket.ignoreSslErrors(expectedSslErrors);
 socket.connectToHostEncrypted("server.tld", 443);

Multiple calls to this function will replace the list of errors that were passed in previous calls. You can clear the list of errors you want to ignore by calling this function with an empty list.

See also sslErrors() and sslHandshakeErrors().

[static, since 6.1] QList<QSsl::ImplementedClass> QSslSocket::implementedClasses(const QString &backendName = {})

This function returns backend-specific classes implemented by the backend named backendName. An empty backendName is understood as a query about the currently active backend.

This function was introduced in Qt 6.1.

See also QSsl::ImplementedClass, activeBackend(), and isClassImplemented().

[static, since 6.1] bool QSslSocket::isClassImplemented(QSsl::ImplementedClass cl, const QString &backendName = {})

Returns true if a class cl is implemented by the backend named backendName. An empty backendName is understood as a query about the currently active backend.

This function was introduced in Qt 6.1.

See also implementedClasses().

bool QSslSocket::isEncrypted() const

Returns true if the socket is encrypted; otherwise, false is returned.

An encrypted socket encrypts all data that is written by calling write() or putChar() before the data is written to the network, and decrypts all incoming data as the data is received from the network, before you call read(), readLine() or getChar().

QSslSocket emits encrypted() when it enters encrypted mode.

You can call sessionCipher() to find which cryptographic cipher is used to encrypt and decrypt your data.

See also mode().

[static, since 6.1] bool QSslSocket::isFeatureSupported(QSsl::SupportedFeature ft, const QString &backendName = {})

Returns true if a feature ft is supported by a backend named backendName. An empty backendName is understood as a query about the currently active backend.

This function was introduced in Qt 6.1.

See also QSsl::SupportedFeature and supportedFeatures().

[static, since 6.1] bool QSslSocket::isProtocolSupported(QSsl::SslProtocol protocol, const QString &backendName = {})

Returns true if protocol is supported by a backend named backendName. An empty backendName is understood as a query about the currently active backend.

This function was introduced in Qt 6.1.

See also supportedProtocols().

QSslCertificate QSslSocket::localCertificate() const

Returns the socket's local certificate, or an empty certificate if no local certificate has been assigned.

See also setLocalCertificate() and privateKey().

QList<QSslCertificate> QSslSocket::localCertificateChain() const

Returns the socket's local certificate chain, or an empty list if no local certificates have been assigned.

See also setLocalCertificateChain().

QSslSocket::SslMode QSslSocket::mode() const

Returns the current mode for the socket; either UnencryptedMode, where QSslSocket behaves identially to QTcpSocket, or one of SslClientMode or SslServerMode, where the client is either negotiating or in encrypted mode.

When the mode changes, QSslSocket emits modeChanged()

See also SslMode.

[signal] void QSslSocket::modeChanged(QSslSocket::SslMode mode)

This signal is emitted when QSslSocket changes from QSslSocket::UnencryptedMode to either QSslSocket::SslClientMode or QSslSocket::SslServerMode. mode is the new mode.

See also QSslSocket::mode().

[signal] void QSslSocket::newSessionTicketReceived()

If TLS 1.3 protocol was negotiated during a handshake, QSslSocket emits this signal after receiving NewSessionTicket message. Session and session ticket's lifetime hint are updated in the socket's configuration. The session can be used for session resumption (and a shortened handshake) in future TLS connections.

See also QSslSocket::sslConfiguration(), QSslConfiguration::sessionTicket(), and QSslConfiguration::sessionTicketLifeTimeHint().

QList<QOcspResponse> QSslSocket::ocspResponses() const

This function returns Online Certificate Status Protocol responses that a server may send during a TLS handshake using OCSP stapling. The list is empty if no definitive response or no response at all was received.

See also QSslConfiguration::setOcspStaplingEnabled().

QSslCertificate QSslSocket::peerCertificate() const

Returns the peer's digital certificate (i.e., the immediate certificate of the host you are connected to), or a null certificate, if the peer has not assigned a certificate.

The peer certificate is checked automatically during the handshake phase, so this function is normally used to fetch the certificate for display or for connection diagnostic purposes. It contains information about the peer, including its host name, the certificate issuer, and the peer's public key.

Because the peer certificate is set during the handshake phase, it is safe to access the peer certificate from a slot connected to the sslErrors() signal or the encrypted() signal.

If a null certificate is returned, it can mean the SSL handshake failed, or it can mean the host you are connected to doesn't have a certificate, or it can mean there is no connection.

If you want to check the peer's complete chain of certificates, use peerCertificateChain() to get them all at once.

See also peerCertificateChain().

QList<QSslCertificate> QSslSocket::peerCertificateChain() const

Returns the peer's chain of digital certificates, or an empty list of certificates.

Peer certificates are checked automatically during the handshake phase. This function is normally used to fetch certificates for display, or for performing connection diagnostics. Certificates contain information about the peer and the certificate issuers, including host name, issuer names, and issuer public keys.

The peer certificates are set in QSslSocket during the handshake phase, so it is safe to call this function from a slot connected to the sslErrors() signal or the encrypted() signal.

If an empty list is returned, it can mean the SSL handshake failed, or it can mean the host you are connected to doesn't have a certificate, or it can mean there is no connection.

If you want to get only the peer's immediate certificate, use peerCertificate().

See also peerCertificate().

int QSslSocket::peerVerifyDepth() const

Returns the maximum number of certificates in the peer's certificate chain to be checked during the SSL handshake phase, or 0 (the default) if no maximum depth has been set, indicating that the whole certificate chain should be checked.

The certificates are checked in issuing order, starting with the peer's own certificate, then its issuer's certificate, and so on.

See also setPeerVerifyDepth() and peerVerifyMode().

[signal] void QSslSocket::peerVerifyError(const QSslError &error)

QSslSocket can emit this signal several times during the SSL handshake, before encryption has been established, to indicate that an error has occurred while establishing the identity of the peer. The error is usually an indication that QSslSocket is unable to securely identify the peer.

This signal provides you with an early indication when something's wrong. By connecting to this signal, you can manually choose to tear down the connection from inside the connected slot before the handshake has completed. If no action is taken, QSslSocket will proceed to emitting QSslSocket::sslErrors().

See also sslErrors().

QSslSocket::PeerVerifyMode QSslSocket::peerVerifyMode() const

Returns the socket's verify mode. This mode decides whether QSslSocket should request a certificate from the peer (i.e., the client requests a certificate from the server, or a server requesting a certificate from the client), and whether it should require that this certificate is valid.

The default mode is AutoVerifyPeer, which tells QSslSocket to use VerifyPeer for clients and QueryPeer for servers.

See also setPeerVerifyMode(), peerVerifyDepth(), and mode().

QString QSslSocket::peerVerifyName() const

Returns the different hostname for the certificate validation, as set by setPeerVerifyName or by connectToHostEncrypted.

See also setPeerVerifyName() and connectToHostEncrypted().

[signal] void QSslSocket::preSharedKeyAuthenticationRequired(QSslPreSharedKeyAuthenticator *authenticator)

QSslSocket emits this signal when it negotiates a PSK ciphersuite, and therefore a PSK authentication is then required.

When using PSK, the client must send to the server a valid identity and a valid pre shared key, in order for the SSL handshake to continue. Applications can provide this information in a slot connected to this signal, by filling in the passed authenticator object according to their needs.

See also QSslPreSharedKeyAuthenticator.

QSslKey QSslSocket::privateKey() const

Returns this socket's private key.

See also setPrivateKey() and localCertificate().

QSsl::SslProtocol QSslSocket::protocol() const

Returns the socket's SSL protocol. By default, QSsl::SecureProtocols is used.

See also setProtocol().

[override virtual protected] qint64 QSslSocket::readData(char *data, qint64 maxlen)

Reimplements: QAbstractSocket::readData(char *data, qint64 maxSize).

[override virtual] void QSslSocket::resume()

Reimplements: QAbstractSocket::resume().

Continues data transfer on the socket after it has been paused. If "setPauseMode(QAbstractSocket::PauseOnSslErrors);" has been called on this socket and a sslErrors() signal is received, calling this method is necessary for the socket to continue.

See also QAbstractSocket::pauseMode() and QAbstractSocket::setPauseMode().

QSslCipher QSslSocket::sessionCipher() const

Returns the socket's cryptographic cipher, or a null cipher if the connection isn't encrypted. The socket's cipher for the session is set during the handshake phase. The cipher is used to encrypt and decrypt data transmitted through the socket.

QSslSocket also provides functions for setting the ordered list of ciphers from which the handshake phase will eventually select the session cipher. This ordered list must be in place before the handshake phase begins.

See also QSslConfiguration::ciphers(), QSslConfiguration::setCiphers(), QSslConfiguration::setCiphers(), QSslConfiguration::ciphers(), and QSslConfiguration::supportedCiphers().

QSsl::SslProtocol QSslSocket::sessionProtocol() const

Returns the socket's SSL/TLS protocol or UnknownProtocol if the connection isn't encrypted. The socket's protocol for the session is set during the handshake phase.

See also protocol() and setProtocol().

[static, since 6.1] bool QSslSocket::setActiveBackend(const QString &backendName)

Returns true if a backend with name backendName was set as active backend. backendName must be one of names returned by availableBackends().

This function was introduced in Qt 6.1.

See also activeBackend() and availableBackends().

void QSslSocket::setLocalCertificate(const QSslCertificate &certificate)

Sets the socket's local certificate to certificate. The local certificate is necessary if you need to confirm your identity to the peer. It is used together with the private key; if you set the local certificate, you must also set the private key.

The local certificate and private key are always necessary for server sockets, but are also rarely used by client sockets if the server requires the client to authenticate.

See also localCertificate() and setPrivateKey().

void QSslSocket::setLocalCertificate(const QString &path, QSsl::EncodingFormat format = QSsl::Pem)

This is an overloaded function.

Sets the socket's local certificate to the first one found in file path, which is parsed according to the specified format.

void QSslSocket::setLocalCertificateChain(const QList<QSslCertificate> &localChain)

Sets the certificate chain to be presented to the peer during the SSL handshake to be localChain.

See also localCertificateChain() and QSslConfiguration::setLocalCertificateChain().

void QSslSocket::setPeerVerifyDepth(int depth)

Sets the maximum number of certificates in the peer's certificate chain to be checked during the SSL handshake phase, to depth. Setting a depth of 0 means that no maximum depth is set, indicating that the whole certificate chain should be checked.

The certificates are checked in issuing order, starting with the peer's own certificate, then its issuer's certificate, and so on.

See also peerVerifyDepth() and setPeerVerifyMode().

void QSslSocket::setPeerVerifyMode(QSslSocket::PeerVerifyMode mode)

Sets the socket's verify mode to mode. This mode decides whether QSslSocket should request a certificate from the peer (i.e., the client requests a certificate from the server, or a server requesting a certificate from the client), and whether it should require that this certificate is valid.

The default mode is AutoVerifyPeer, which tells QSslSocket to use VerifyPeer for clients and QueryPeer for servers.

Setting this mode after encryption has started has no effect on the current connection.

See also peerVerifyMode(), setPeerVerifyDepth(), and mode().

void QSslSocket::setPeerVerifyName(const QString &hostName)

Sets a different host name, given by hostName, for the certificate validation instead of the one used for the TCP connection.

See also peerVerifyName() and connectToHostEncrypted().

void QSslSocket::setPrivateKey(const QSslKey &key)

Sets the socket's private key to key. The private key and the local certificate are used by clients and servers that must prove their identity to SSL peers.

Both the key and the local certificate are required if you are creating an SSL server socket. If you are creating an SSL client socket, the key and local certificate are required if your client must identify itself to an SSL server.

See also privateKey() and setLocalCertificate().

void QSslSocket::setPrivateKey(const QString &fileName, QSsl::KeyAlgorithm algorithm = QSsl::Rsa, QSsl::EncodingFormat format = QSsl::Pem, const QByteArray &passPhrase = QByteArray())

This is an overloaded function.

Reads the string in file fileName and decodes it using a specified algorithm and encoding format to construct an SSL key. If the encoded key is encrypted, passPhrase is used to decrypt it.

The socket's private key is set to the constructed key. The private key and the local certificate are used by clients and servers that must prove their identity to SSL peers.

Both the key and the local certificate are required if you are creating an SSL server socket. If you are creating an SSL client socket, the key and local certificate are required if your client must identify itself to an SSL server.

See also privateKey() and setLocalCertificate().

void QSslSocket::setProtocol(QSsl::SslProtocol protocol)

Sets the socket's SSL protocol to protocol. This will affect the next initiated handshake; calling this function on an already-encrypted socket will not affect the socket's protocol.

See also protocol().

[override virtual] void QSslSocket::setReadBufferSize(qint64 size)

Reimplements: QAbstractSocket::setReadBufferSize(qint64 size).

Sets the size of QSslSocket's internal read buffer to be size bytes.

[override virtual] bool QSslSocket::setSocketDescriptor(qintptr socketDescriptor, QAbstractSocket::SocketState state = ConnectedState, QIODeviceBase::OpenMode openMode = ReadWrite)

Reimplements: QAbstractSocket::setSocketDescriptor(qintptr socketDescriptor, QAbstractSocket::SocketState socketState, QIODeviceBase::OpenMode openMode).

Initializes QSslSocket with the native socket descriptor socketDescriptor. Returns true if socketDescriptor is accepted as a valid socket descriptor; otherwise returns false. The socket is opened in the mode specified by openMode, and enters the socket state specified by state.

See also socketDescriptor().

[override virtual] void QSslSocket::setSocketOption(QAbstractSocket::SocketOption option, const QVariant &value)

Reimplements: QAbstractSocket::setSocketOption(QAbstractSocket::SocketOption option, const QVariant &value).

Sets the given option to the value described by value.

See also socketOption().

void QSslSocket::setSslConfiguration(const QSslConfiguration &configuration)

Sets the socket's SSL configuration to be the contents of configuration. This function sets the local certificate, the ciphers, the private key and the CA certificates to those stored in configuration.

It is not possible to set the SSL-state related fields.

See also sslConfiguration(), setLocalCertificate(), setPrivateKey(), QSslConfiguration::setCaCertificates(), and QSslConfiguration::setCiphers().

[override virtual protected] qint64 QSslSocket::skipData(qint64 maxSize)

Reimplements: QAbstractSocket::skipData(qint64 maxSize).

[override virtual] QVariant QSslSocket::socketOption(QAbstractSocket::SocketOption option)

Reimplements: QAbstractSocket::socketOption(QAbstractSocket::SocketOption option).

Returns the value of the option option.

See also setSocketOption().

QSslConfiguration QSslSocket::sslConfiguration() const

Returns the socket's SSL configuration state. The default SSL configuration of a socket is to use the default ciphers, default CA certificates, no local private key or certificate.

The SSL configuration also contains fields that can change with time without notice.

See also setSslConfiguration(), localCertificate(), peerCertificate(), peerCertificateChain(), sessionCipher(), privateKey(), QSslConfiguration::ciphers(), and QSslConfiguration::caCertificates().

[signal] void QSslSocket::sslErrors(const QList<QSslError> &errors)

QSslSocket emits this signal after the SSL handshake to indicate that one or more errors have occurred while establishing the identity of the peer. The errors are usually an indication that QSslSocket is unable to securely identify the peer. Unless any action is taken, the connection will be dropped after this signal has been emitted.

If you want to continue connecting despite the errors that have occurred, you must call QSslSocket::ignoreSslErrors() from inside a slot connected to this signal. If you need to access the error list at a later point, you can call sslHandshakeErrors().

errors contains one or more errors that prevent QSslSocket from verifying the identity of the peer.

See also peerVerifyError().

QList<QSslError> QSslSocket::sslHandshakeErrors() const

Returns a list of the last SSL errors that occurred. This is the same list as QSslSocket passes via the sslErrors() signal. If the connection has been encrypted with no errors, this function will return an empty list.

See also connectToHostEncrypted().

[static] long QSslSocket::sslLibraryBuildVersionNumber()

Returns the version number of the SSL library in use at compile time. If no SSL support is available then this will return -1.

See also sslLibraryVersionNumber().

[static] QString QSslSocket::sslLibraryBuildVersionString()

Returns the version string of the SSL library in use at compile time. If no SSL support is available then this will return an empty value.

See also sslLibraryVersionString().

[static] long QSslSocket::sslLibraryVersionNumber()

Returns the version number of the SSL library in use. Note that this is the version of the library in use at run-time not compile time. If no SSL support is available then this will return -1.

[static] QString QSslSocket::sslLibraryVersionString()

Returns the version string of the SSL library in use. Note that this is the version of the library in use at run-time not compile time. If no SSL support is available then this will return an empty value.

[slot] void QSslSocket::startClientEncryption()

Starts a delayed SSL handshake for a client connection. This function can be called when the socket is in the ConnectedState but still in the UnencryptedMode. If it is not yet connected, or if it is already encrypted, this function has no effect.

Clients that implement STARTTLS functionality often make use of delayed SSL handshakes. Most other clients can avoid calling this function directly by using connectToHostEncrypted() instead, which automatically performs the handshake.

See also connectToHostEncrypted() and startServerEncryption().

[slot] void QSslSocket::startServerEncryption()

Starts a delayed SSL handshake for a server connection. This function can be called when the socket is in the ConnectedState but still in UnencryptedMode. If it is not connected or it is already encrypted, the function has no effect.

For server sockets, calling this function is the only way to initiate the SSL handshake. Most servers will call this function immediately upon receiving a connection, or as a result of having received a protocol-specific command to enter SSL mode (e.g, the server may respond to receiving the string "STARTTLS\r\n" by calling this function).

The most common way to implement an SSL server is to create a subclass of QTcpServer and reimplement QTcpServer::incomingConnection(). The returned socket descriptor is then passed to QSslSocket::setSocketDescriptor().

See also connectToHostEncrypted() and startClientEncryption().

[static, since 6.1] QList<QSsl::SupportedFeature> QSslSocket::supportedFeatures(const QString &backendName = {})

This function returns features supported by a backend named backendName. An empty backendName is understood as a query about the currently active backend.

This function was introduced in Qt 6.1.

See also QSsl::SupportedFeature and activeBackend().

[static, since 6.1] QList<QSsl::SslProtocol> QSslSocket::supportedProtocols(const QString &backendName = {})

If a backend with name backendName is available, this function returns the list of TLS protocol versions supported by this backend. An empty backendName is understood as a query about the currently active backend. Otherwise, this function returns an empty list.

This function was introduced in Qt 6.1.

See also availableBackends(), activeBackend(), and isProtocolSupported().

[static] bool QSslSocket::supportsSsl()

Returns true if this platform supports SSL; otherwise, returns false. If the platform doesn't support SSL, the socket will fail in the connection phase.

[override virtual] bool QSslSocket::waitForBytesWritten(int msecs = 30000)

Reimplements: QAbstractSocket::waitForBytesWritten(int msecs).

[override virtual] bool QSslSocket::waitForConnected(int msecs = 30000)

Reimplements: QAbstractSocket::waitForConnected(int msecs).

Waits until the socket is connected, or msecs milliseconds, whichever happens first. If the connection has been established, this function returns true; otherwise it returns false.

See also QAbstractSocket::waitForConnected().

[override virtual] bool QSslSocket::waitForDisconnected(int msecs = 30000)

Reimplements: QAbstractSocket::waitForDisconnected(int msecs).

Waits until the socket has disconnected or msecs milliseconds, whichever comes first. If the connection has been disconnected, this function returns true; otherwise it returns false.

See also QAbstractSocket::waitForDisconnected().

bool QSslSocket::waitForEncrypted(int msecs = 30000)

Waits until the socket has completed the SSL handshake and has emitted encrypted(), or msecs milliseconds, whichever comes first. If encrypted() has been emitted, this function returns true; otherwise (e.g., the socket is disconnected, or the SSL handshake fails), false is returned.

The following example waits up to one second for the socket to be encrypted:

 socket->connectToHostEncrypted("imap", 993);
 if (socket->waitForEncrypted(1000))
     qDebug("Encrypted!");

If msecs is -1, this function will not time out.

See also startClientEncryption(), startServerEncryption(), encrypted(), and isEncrypted().

[override virtual] bool QSslSocket::waitForReadyRead(int msecs = 30000)

Reimplements: QAbstractSocket::waitForReadyRead(int msecs).

[override virtual protected] qint64 QSslSocket::writeData(const char *data, qint64 len)

Reimplements: QAbstractSocket::writeData(const char *data, qint64 size).