QWebSocket Class

See also QAbstractSocket, QTcpSocket, QWebSocket client example

Creates a new QWebSocket with the given origin, the version of the protocol to use and parent.

The origin of the client is as specified in RFC 6454. (The origin is not required for non-web browser clients (see RFC 6455)). The origin may not contain new line characters, otherwise the connection will be aborted immediately during the handshake phase.

Destroys the QWebSocket. Closes the socket if it is still open, and releases any used resources.

Aborts the current socket and resets the socket. Unlike close(), this function immediately closes the socket, discarding any pending data in the write buffer.

This signal is emitted when the socket is about to close. Connect this signal if you have operations that need to be performed before the socket closes (e.g., if you have data in a separate buffer that needs to be written to the device).

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QWebSocket 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.

This function was introduced in Qt 6.2.

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QWebSocket 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.

This function was introduced in Qt 6.2.

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This signal is emitted whenever a binary frame is received. The frame contains the data and isLastFrame indicates whether this is the last frame of the complete message.

This signal can be used to process large messages frame by frame, instead of waiting for the complete message to arrive.

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This signal is emitted whenever a binary message is received. The message contains the received bytes.

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Returns the number of bytes that are waiting to be written. The bytes are written when control goes back to the event loop or when flush() is called.

This function was introduced in Qt 5.12.

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This signal is emitted every time a payload of data has been written to the socket. The bytes argument is set to the number of bytes that were written in this payload.

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Gracefully closes the socket with the given closeCode and reason.

Any data in the write buffer is flushed before the socket is closed. The closeCode is a QWebSocketProtocol::CloseCode indicating the reason to close, and reason describes the reason of the closure more in detail. All control frames, including the Close frame, are limited to 125 bytes. Since two of these are used for closeCode the maximum length of reason is 123! If reason exceeds this limit it will be truncated.

Returns the code indicating why the socket was closed.

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Returns the reason why the socket was closed.

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Emitted when a connection is successfully established. A connection is successfully established when the socket is connected and the handshake was successful.

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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 6.2.

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Emitted when the socket is disconnected.

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Returns the type of error that last occurred

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This signal is emitted after an error occurred. The error parameter describes the type of error that occurred.

QAbstractSocket::SocketError is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType().

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Returns a human-readable description of the last error that occurred

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This function writes as much as possible from the internal write buffer to the underlying network socket, without blocking. If any data was written, this function returns true; otherwise false is returned. Call this function if you need QWebSocket to start sending buffered data immediately. The number of bytes successfully written depends on the operating system. In most cases, you do not need to call this function, because QWebSocket will start sending data automatically once control goes back to the event loop.

QWebSocket 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.

This function was introduced in Qt 6.2.

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Returns the handshake options that were used to open this socket.

This function was introduced in Qt 6.4.

This slot tells QWebSocket to ignore errors during QWebSocket'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.

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This is an overloaded function.

This method tells QWebSocket to ignore the errors given in errors.

Note that you can set the expected certificate in the SSL error: If, for instance, you want to connect to a server that uses a self-signed certificate, consider the following snippet:

QList<QSslCertificate> cert = QSslCertificate::fromPath(QLatin1String("server-certificate.pem"));
QSslError error(QSslError::SelfSignedCertificate, cert.at(0));
QList<QSslError> expectedSslErrors;
expectedSslErrors.append(error);

QWebSocket socket;
socket.ignoreSslErrors(expectedSslErrors);
socket.open(QUrl(QStringLiteral("wss://myserver.at.home")));

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.

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Returns true if the socket is ready for reading and writing; otherwise returns false.

Returns the local address

Returns the local port

Returns the mask generator that is currently used by this QWebSocket.

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Returns the maximum allowed size of an incoming websocket frame.

This function was introduced in Qt 5.15.

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Returns the maximum allowed size of an incoming websocket message.

This function was introduced in Qt 5.15.

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Returns the maximum supported size of an incoming websocket frame for this websocket implementation.

This function was introduced in Qt 5.15.

Returns the maximum supported size of an incoming websocket message for this websocket implementation.

This function was introduced in Qt 5.15.

Returns the maximum supported size of an outgoing websocket frame for this websocket implementation.

This function was introduced in Qt 5.15.

Opens a WebSocket connection using the given url.

If the url contains newline characters (\r\n), then the error signal will be emitted with QAbstractSocket::ConnectionRefusedError as error type.

Opens a WebSocket connection using the given request.

The request url will be used to open the WebSocket connection. Headers present in the request will be sent to the server in the upgrade request, together with the ones needed for the websocket handshake.

This function was introduced in Qt 5.6.

Opens a WebSocket connection using the given url and options.

If the url contains newline characters (\r\n), then the error signal will be emitted with QAbstractSocket::ConnectionRefusedError as error type.

Additional options for the WebSocket handshake such as subprotocols can be specified in options.

This function was introduced in Qt 6.4.

Opens a WebSocket connection using the given request and options.

The request url will be used to open the WebSocket connection. Headers present in the request will be sent to the server in the upgrade request, together with the ones needed for the websocket handshake.

Additional options for the WebSocket handshake such as subprotocols can be specified in options.

This function was introduced in Qt 6.4.

Returns the current origin.

Returns the maximum size of an outgoing websocket frame.

This function was introduced in Qt 5.15.

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Returns the pause mode of this socket

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Returns the peer address

Returns the peerName

Returns the peerport

QWebSocket 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 QWebSocket 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, QWebSocket will proceed to emitting QWebSocket::sslErrors().

This function was introduced in Qt 6.2.

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Pings the server to indicate that the connection is still alive. Additional payload can be sent along the ping message.

The size of the payload cannot be bigger than 125. If it is larger, the payload is clipped to 125 bytes.

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Emitted when a pong message is received in reply to a previous ping. elapsedTime contains the roundtrip time in milliseconds and payload contains an optional payload that was sent with the ping.

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This signal is emitted if the SSL/TLS handshake 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.

This function was introduced in Qt 5.8.

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Returns the currently configured proxy

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This signal can be emitted when a proxy that requires authentication is used. The authenticator object can then be filled in with the required details to allow authentication and continue the connection.

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Returns the size in bytes of the readbuffer that is used by the socket.

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This signal is emitted when the input (reading) stream is closed in this device. It is emitted as soon as the closing is detected.

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Returns the request that was or will be used to open this socket.

This function was introduced in Qt 5.6.

Returns the url the socket is connected to or will connect to.

Returns the name of the resource currently accessed.

Continues data transfer on the socket. This method should only be used after the socket has been set to pause upon notifications and a notification has been received. The only notification currently supported is sslErrors(). Calling this method if the socket is not paused results in undefined behavior.

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Sends the given data over the socket as a binary message and returns the number of bytes actually sent.

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Sends the given message over the socket as a text message and returns the number of bytes actually sent.

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Sets the generator to use for creating masks to maskGenerator. The default QWebSocket generator can be reset by supplying a nullptr. The mask generator can be changed at any time, even while the connection is open.

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Sets the maximum allowed size of an incoming websocket frame to maxAllowedIncomingFrameSize. If an incoming frame exceeds this limit, the peer gets disconnected. The accepted range is between 0 and maxIncomingFrameSize(), default is maxIncomingFrameSize(). The purpose of this function is to avoid exhausting virtual memory.

This function was introduced in Qt 5.15.

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Sets the maximum allowed size of an incoming websocket message to maxAllowedIncomingMessageSize. If an incoming message exceeds this limit, the peer gets disconnected. The accepted range is between 0 and maxIncomingMessageSize(), default is maxIncomingMessageSize(). The purpose of this function is to avoid exhausting virtual memory.

This function was introduced in Qt 5.15.

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Sets the maximum size of an outgoing websocket frame to outgoingFrameSize. The accepted range is between 0 and maxOutgoingFrameSize(), default is 512kB. The purpose of this function is to adapt to the maximum allowed frame size of the receiver.

This function was introduced in Qt 5.15.

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Controls whether to pause upon receiving a notification. The pauseMode parameter specifies the conditions in which the socket should be paused.

The only notification currently supported is sslErrors(). If set to PauseOnSslErrors, data transfer on the socket will be paused and needs to be enabled explicitly again by calling resume(). By default, this option is set to PauseNever. This option must be called before connecting to the server, otherwise it will result in undefined behavior.

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Sets the proxy to networkProxy

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

If the buffer size is limited to a certain size, QWebSocket won't buffer more than this size of data. Exceptionally, a buffer size of 0 means that the read buffer is unlimited and all incoming data is buffered. This is the default. This option is useful if you only read the data at certain points in time (for example, in a real-time streaming application) or if you want to protect your socket against receiving too much data, which may eventually cause your application to run out of memory.

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Sets the socket's SSL configuration to be the contents of sslConfiguration.

This function sets the local certificate, the ciphers, the private key and the CA certificates to those stored in sslConfiguration. It is not possible to set the SSL-state related fields.

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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.

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QWebSocket 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 QWebSocket 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 QWebSocket::ignoreSslErrors() from inside a slot connected to this signal. If you need to access the error list at a later point, you can call sslErrors() (without arguments).

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

Returns the current state of the socket.

This signal is emitted whenever QWebSocket's state changes. The state parameter is the new state.

QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType().

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Returns the used WebSocket protocol.

This function was introduced in Qt 6.4.

This signal is emitted whenever a text frame is received. The frame contains the data and isLastFrame indicates whether this is the last frame of the complete message.

This signal can be used to process large messages frame by frame, instead of waiting for the complete message to arrive.

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This signal is emitted whenever a text message is received. The message contains the received text.

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Returns the version the socket is currently using.