- Qt 6.10
- Qt WebSockets
- C++ Classes
- QWebSocketServer
- Qt 6.10.2 Reference Documentation

# QWebSocketServer Class

Implements a WebSocket-based server. More...

Header: | `#include <QWebSocketServer>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS WebSockets)` `target_link_libraries(mytarget PRIVATE Qt6::WebSockets)`
qmake: | `QT += websockets`

- List of all members, including inherited members
- Deprecated members

## Public Types

enum | SslMode { SecureMode, NonSecureMode }

## Public Functions

| QWebSocketServer(const QString &serverName, QWebSocketServer::SslMode secureMode, QObject *parent = nullptr)
virtual | ~QWebSocketServer() override
void | close()
QWebSocketProtocol::CloseCode | error() const
QString | errorString() const
void | handleConnection(QTcpSocket *socket) const
std::chrono::milliseconds | handshakeTimeout() const
int | handshakeTimeoutMS() const
bool | hasPendingConnections() const
bool | isListening() const
bool | listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0)
int | maxPendingConnections() const
virtual QWebSocket * | nextPendingConnection()
void | pauseAccepting()
QNetworkProxy | proxy() const
void | resumeAccepting()
QWebSocketServer::SslMode | secureMode() const
QHostAddress | serverAddress() const
QString | serverName() const
quint16 | serverPort() const
QUrl | serverUrl() const
void | setHandshakeTimeout(std::chrono::milliseconds msec)
void | setHandshakeTimeout(int msec)
void | setMaxPendingConnections(int numConnections)
void | setProxy(const QNetworkProxy &networkProxy)
void | setServerName(const QString &serverName)
bool | setSocketDescriptor(qintptr socketDescriptor)
void | setSslConfiguration(const QSslConfiguration &sslConfiguration)
`(since 6.4)` void | setSupportedSubprotocols(const QStringList &protocols)
qintptr | socketDescriptor() const
QSslConfiguration | sslConfiguration() const
`(since 6.4)` QStringList | supportedSubprotocols() const
QList<QWebSocketProtocol::Version> | supportedVersions() const

## Signals

void | acceptError(QAbstractSocket::SocketError socketError)
`(since 6.2)` void | alertReceived(QSsl::AlertLevel level, QSsl::AlertType type, const QString &description)
`(since 6.2)` void | alertSent(QSsl::AlertLevel level, QSsl::AlertType type, const QString &description)
void | closed()
`(since 6.2)` void | handshakeInterruptedOnError(const QSslError &error)
void | newConnection()
void | originAuthenticationRequired(QWebSocketCorsAuthenticator *authenticator)
void | peerVerifyError(const QSslError &error)
void | preSharedKeyAuthenticationRequired(QSslPreSharedKeyAuthenticator *authenticator)
void | serverError(QWebSocketProtocol::CloseCode closeCode)
void | sslErrors(const QList<QSslError> &errors)

## Detailed Description

It is modeled after QTcpServer, and behaves the same. So, if you know how to use QTcpServer, you know how to use QWebSocketServer. This class makes it possible to accept incoming WebSocket connections. You can specify the port or have QWebSocketServer pick one automatically. You can listen on a specific address or on all the machine's addresses. Call listen() to have the server listen for incoming connections.

The newConnection() signal is then emitted each time a client connects to the server. Call nextPendingConnection() to accept the pending connection as a connected QWebSocket. The function returns a pointer to a QWebSocket in QAbstractSocket::ConnectedState that you can use for communicating with the client.

If an error occurs, serverError() returns the type of error, and errorString() can be called to get a human readable description of what happened.

When listening for connections, the address and port on which the server is listening are available as serverAddress() and serverPort().

Calling close() makes QWebSocketServer stop listening for incoming connections.

QWebSocketServer currently does not support WebSocket Extensions.

Note: When working with self-signed certificates, Firefox bug 594502 prevents Firefox to connect to a secure WebSocket server. To work around this problem, first browse to the secure WebSocket server using HTTPS. FireFox will indicate that the certificate is invalid. From here on, the certificate can be added to the exceptions. After this, the secure WebSockets connection should work.

QWebSocketServer only supports version 13 of the WebSocket protocol, as outlined in RFC 6455.

There is a default connection handshake timeout of 10 seconds to avoid denial of service, which can be customized using setHandshakeTimeout().

See also WebSocket Server Example and QWebSocket.

## Member Type Documentation

### enum QWebSocketServer::SslMode

Indicates whether the server operates over wss (SecureMode) or ws (NonSecureMode)

Constant | Value | Description
--- | --- | ---
`QWebSocketServer::SecureMode` | `0` | The server operates in secure mode (over wss)
`QWebSocketServer::NonSecureMode` | `1` | The server operates in non-secure mode (over ws)

## Member Function Documentation

### `[explicit]` QWebSocketServer::QWebSocketServer(const QString &serverName, QWebSocketServer::SslMode secureMode, QObject *parent = nullptr)

Constructs a new QWebSocketServer with the given serverName. The serverName will be used in the HTTP handshake phase to identify the server. It can be empty, in which case no server name will be sent to the client. The secureMode parameter indicates whether the server operates over wss (SecureMode) or over ws (NonSecureMode).

parent is passed to the QObject constructor.

### `[override virtual noexcept]` QWebSocketServer::~QWebSocketServer()

Destroys the QWebSocketServer object. If the server is listening for connections, the socket is automatically closed. Any client QWebSockets that are still queued are closed and deleted.

See also close().

### `[signal]` void QWebSocketServer::acceptError(QAbstractSocket::SocketError socketError)

This signal is emitted when the acceptance of a new connection results in an error. The socketError parameter describes the type of error that occurred.

See also pauseAccepting() and resumeAccepting().

### `[signal, since 6.2]` void QWebSocketServer::alertReceived(QSsl::AlertLevel level, QSsl::AlertType type, const QString &description)

QWebSocketServer 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.

Note: The signal is mostly for informational and debugging purposes and does not require any handling in the application. If the alert was fatal, underlying backend will handle it and close the connection.

Note: Not all backends support this functionality.

This function was introduced in Qt 6.2.

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

### `[signal, since 6.2]` void QWebSocketServer::alertSent(QSsl::AlertLevel level, QSsl::AlertType type, const QString &description)

QWebSocketServer 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.

Note: This signal is mostly informational and can be used for debugging purposes, normally it does not require any actions from the application.

Note: Not all backends support this functionality.

This function was introduced in Qt 6.2.

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

### void QWebSocketServer::close()

Closes the server. The server will no longer listen for incoming connections.

### `[signal]` void QWebSocketServer::closed()

This signal is emitted when the server closed its connection.

See also close().

### QWebSocketProtocol::CloseCode QWebSocketServer::error() const

Returns an error code for the last error that occurred. If no error occurred, QWebSocketProtocol::CloseCodeNormal is returned.

See also errorString().

### QString QWebSocketServer::errorString() const

Returns a human readable description of the last error that occurred. If no error occurred, an empty string is returned.

See also serverError().

### void QWebSocketServer::handleConnection(QTcpSocket *socket) const

Upgrades a tcp socket to websocket.

The QWebSocketServer object will take ownership of the socket object and delete it when appropriate.

### `[signal, since 6.2]` void QWebSocketServer::handshakeInterruptedOnError(const QSslError &error)

QWebSocketServer emits this signal if a certificate verification error was found and if early error reporting was enabled in QSslConfiguration.

This function was introduced in Qt 6.2.

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

### std::chrono::milliseconds QWebSocketServer::handshakeTimeout() const

Returns the handshake timeout for new connections in milliseconds.

The default is 10 seconds. If a peer uses more time to complete the handshake their connection is closed.

See also setHandshakeTimeout() and handshakeTimeoutMS().

### int QWebSocketServer::handshakeTimeoutMS() const

Returns the handshake timeout for new connections in milliseconds.

The default is 10 seconds. If a peer uses more time to complete the handshake their connection is closed.

See also setHandshakeTimeout() and handshakeTimeout().

### bool QWebSocketServer::hasPendingConnections() const

Returns true if the server has pending connections; otherwise returns false.

See also nextPendingConnection() and setMaxPendingConnections().

### bool QWebSocketServer::isListening() const

Returns true if the server is currently listening for incoming connections; otherwise returns false. If listening fails, error() will return the reason.

See also listen() and error().

### bool QWebSocketServer::listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0)

Tells the server to listen for incoming connections on address address and port port. If port is 0, a port is chosen automatically. If address is QHostAddress::Any, the server will listen on all network interfaces.

Returns true on success; otherwise returns false.

See also isListening().

### int QWebSocketServer::maxPendingConnections() const

Returns the maximum number of pending accepted connections. The default is 30.

See also setMaxPendingConnections() and hasPendingConnections().

### `[signal]` void QWebSocketServer::newConnection()

This signal is emitted every time a new connection is available.

See also hasPendingConnections() and nextPendingConnection().

### `[virtual]` QWebSocket *QWebSocketServer::nextPendingConnection()

Returns the next pending connection as a connected QWebSocket object. QWebSocketServer does not take ownership of the returned QWebSocket object. It is up to the caller to delete the object explicitly when it will no longer be used, otherwise a memory leak will occur. nullptr is returned if this function is called when there are no pending connections.

Note: The returned QWebSocket object cannot be used from another thread.

See also hasPendingConnections().

### `[signal]` void QWebSocketServer::originAuthenticationRequired(QWebSocketCorsAuthenticator *authenticator)

This signal is emitted when a new connection is requested. The slot connected to this signal should indicate whether the origin (which can be determined by the origin() call) is allowed in the authenticator object (by issuing setAllowed()).

If no slot is connected to this signal, all origins will be accepted by default.

Note: It is not possible to use a QueuedConnection to connect to this signal, as the connection will always succeed.

### void QWebSocketServer::pauseAccepting()

Pauses incoming new connections. Queued connections will remain in queue.

See also resumeAccepting().

### `[signal]` void QWebSocketServer::peerVerifyError(const QSslError &error)

QWebSocketServer 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 QWebSocketServer is unable to securely identify the peer.

This signal provides you with an early indication when something is 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, QWebSocketServer will proceed to emitting QWebSocketServer::sslErrors().

See also sslErrors().

### `[signal]` void QWebSocketServer::preSharedKeyAuthenticationRequired(QSslPreSharedKeyAuthenticator *authenticator)

QWebSocketServer 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.

Note: Ignoring this signal, or failing to provide the required credentials, will cause the handshake to fail, and therefore the connection to be aborted.

Note: The authenticator object is owned by the socket and must not be deleted by the application.

See also QSslPreSharedKeyAuthenticator and QSslSocket::preSharedKeyAuthenticationRequired().

### QNetworkProxy QWebSocketServer::proxy() const

Returns the network proxy for this server. By default QNetworkProxy::DefaultProxy is used.

See also setProxy().

### void QWebSocketServer::resumeAccepting()

Resumes accepting new connections.

See also pauseAccepting().

### QWebSocketServer::SslMode QWebSocketServer::secureMode() const

Returns the secure mode the server is running in.

See also QWebSocketServer() and SslMode.

### QHostAddress QWebSocketServer::serverAddress() const

Returns the server's address if the server is listening for connections; otherwise returns QHostAddress::Null.

See also serverPort() and listen().

### `[signal]` void QWebSocketServer::serverError(QWebSocketProtocol::CloseCode closeCode)

This signal is emitted when an error occurs during the setup of a WebSocket connection. The closeCode parameter describes the type of error that occurred

See also errorString().

### QString QWebSocketServer::serverName() const

Returns the server name that is used during the http handshake phase.

See also setServerName().

### quint16 QWebSocketServer::serverPort() const

Returns the server's port if the server is listening for connections; otherwise returns 0.

See also serverAddress() and listen().

### QUrl QWebSocketServer::serverUrl() const

Returns a URL clients can use to connect to this server if the server is listening for connections. Otherwise an invalid URL is returned.

See also serverPort(), serverAddress(), and listen().

### void QWebSocketServer::setHandshakeTimeout(std::chrono::milliseconds msec)

Sets the handshake timeout for new connections to msec milliseconds.

By default this is set to 10 seconds. If a peer uses more time to complete the handshake, their connection is closed. You can pass a negative value (e.g. -1) to disable the timeout.

See also handshakeTimeout() and handshakeTimeoutMS().

### void QWebSocketServer::setHandshakeTimeout(int msec)

This is an overloaded function.

### void QWebSocketServer::setMaxPendingConnections(int numConnections)

Sets the maximum number of pending accepted connections to numConnections. WebSocketServer will accept no more than numConnections incoming connections before nextPendingConnection() is called. By default, the limit is 30 pending connections.

QWebSocketServer will emit the error() signal with the QWebSocketProtocol::CloseCodeAbnormalDisconnection close code when the maximum of connections has been reached. The WebSocket handshake will fail and the socket will be closed.

See also maxPendingConnections() and hasPendingConnections().

### void QWebSocketServer::setProxy(const QNetworkProxy &networkProxy)

Sets the explicit network proxy for this server to networkProxy.

To disable the use of a proxy, use the QNetworkProxy::NoProxy proxy type:

     server->setProxy(QNetworkProxy::NoProxy);

See also proxy().

### void QWebSocketServer::setServerName(const QString &serverName)

Sets the server name that will be used during the HTTP handshake phase to the given serverName. The serverName can be empty, in which case an empty server name will be sent to the client. Existing connected clients will not be notified of this change, only newly connecting clients will see this new name.

See also serverName().

### bool QWebSocketServer::setSocketDescriptor(qintptr socketDescriptor)

Sets the socket descriptor this server should use when listening for incoming connections to socketDescriptor.

Returns true if the socket is set successfully; otherwise returns false. The socket is assumed to be in listening state.

See also socketDescriptor() and isListening().

### void QWebSocketServer::setSslConfiguration(const QSslConfiguration &sslConfiguration)

Sets the SSL configuration for the QWebSocketServer to sslConfiguration. This method has no effect if QWebSocketServer runs in non-secure mode (QWebSocketServer::NonSecureMode).

See also sslConfiguration() and SslMode.

### `[since 6.4]` void QWebSocketServer::setSupportedSubprotocols(const QStringList &protocols)

Sets the list of protocols supported by the server to protocols.

This function was introduced in Qt 6.4.

See also supportedSubprotocols().

### qintptr QWebSocketServer::socketDescriptor() const

Returns the native socket descriptor the server uses to listen for incoming instructions, or -1 if the server is not listening. If the server is using QNetworkProxy, the returned descriptor may not be usable with native socket functions.

See also setSocketDescriptor() and isListening().

### QSslConfiguration QWebSocketServer::sslConfiguration() const

Returns the SSL configuration used by the QWebSocketServer. If the server is not running in secure mode (QWebSocketServer::SecureMode), this method returns QSslConfiguration::defaultConfiguration().

See also setSslConfiguration(), SslMode, and QSslConfiguration::defaultConfiguration().

### `[signal]` void QWebSocketServer::sslErrors(const QList<QSslError> &errors)

QWebSocketServer 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 QWebSocketServer is unable to securely identify the peer. Unless any action is taken, the connection will be dropped after this signal has been emitted.

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

See also peerVerifyError().

### `[since 6.4]` QStringList QWebSocketServer::supportedSubprotocols() const

Returns the list of protocols supported by the server.

This function was introduced in Qt 6.4.

See also setSupportedSubprotocols().

### QList<QWebSocketProtocol::Version> QWebSocketServer::supportedVersions() const

Returns a list of WebSocket versions that this server is supporting.