QNetworkAccessManager Class

 QNetworkAccessManager *manager = new QNetworkAccessManager(this);
 connect(manager, &QNetworkAccessManager::finished,
         this, &MyClass::replyFinished);

 manager->get(QNetworkRequest(QUrl("http://qt-project.org")));

 QNetworkRequest request;
 request.setUrl(QUrl("http://qt-project.org"));
 request.setRawHeader("User-Agent", "MyOwnBrowser 1.0");

 QNetworkReply *reply = manager->get(request);
 connect(reply, &QIODevice::readyRead, this, &MyClass::slotReadyRead);
 connect(reply, &QNetworkReply::errorOccurred,
         this, &MyClass::slotError);
 connect(reply, &QNetworkReply::sslErrors,
         this, &MyClass::slotSslErrors);

Member Function Documentation

QNetworkAccessManager::QNetworkAccessManager(QObject *parent = nullptr)

Constructs a QNetworkAccessManager object that is the center of the Network Access API and sets parent as the parent object.

[signal] void QNetworkAccessManager::authenticationRequired(QNetworkReply *reply, QAuthenticator *authenticator)

This signal is emitted whenever a final server requests authentication before it delivers the requested contents. The slot connected to this signal should fill the credentials for the contents (which can be determined by inspecting the reply object) in the authenticator object.

QNetworkAccessManager will cache the credentials internally and will send the same values if the server requires authentication again, without emitting the authenticationRequired() signal. If it rejects the credentials, this signal will be emitted again.

Note: To have the request not send credentials you must not call setUser() or setPassword() on the authenticator object. This will result in the finished() signal being emitted with a QNetworkReply with error AuthenticationRequiredError.

Note: It is not possible to use a QueuedConnection to connect to this signal, as the connection will fail if the authenticator has not been filled in with new information when the signal returns.

See also proxyAuthenticationRequired(), QAuthenticator::setUser(), and QAuthenticator::setPassword().

[signal, since 5.1] void QNetworkAccessManager::encrypted(QNetworkReply *reply)

This signal is emitted when an SSL/TLS session has successfully completed the initial handshake. At this point, no user data has been transmitted. The signal can be used to perform additional checks on the certificate chain, for example to notify users when the certificate for a website has changed. The reply parameter specifies which network reply is responsible. If the reply does not match the expected criteria then it should be aborted by calling QNetworkReply::abort() by a slot connected to this signal. The SSL configuration in use can be inspected using the QNetworkReply::sslConfiguration() method.

Internally, QNetworkAccessManager may open multiple connections to a server, in order to allow it process requests in parallel. These connections may be reused, which means that the encrypted() signal would not be emitted. This means that you are only guaranteed to receive this signal for the first connection to a site in the lifespan of the QNetworkAccessManager.

This function was introduced in Qt 5.1.

See also QSslSocket::encrypted() and QNetworkReply::encrypted().

[signal] void QNetworkAccessManager::finished(QNetworkReply *reply)

This signal is emitted whenever a pending network reply is finished. The reply parameter will contain a pointer to the reply that has just finished. This signal is emitted in tandem with the QNetworkReply::finished() signal.

See QNetworkReply::finished() for information on the status that the object will be in.

Note: Do not delete the reply object in the slot connected to this signal. Use deleteLater().

See also QNetworkReply::finished() and QNetworkReply::error().

[signal, since 5.5] void QNetworkAccessManager::preSharedKeyAuthenticationRequired(QNetworkReply *reply, QSslPreSharedKeyAuthenticator *authenticator)

This signal is emitted if the SSL/TLS handshake negotiates a PSK ciphersuite, and therefore a PSK authentication is then required. The reply object is the QNetworkReply that is negotiating such ciphersuites.

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 reply and must not be deleted by the application.

This function was introduced in Qt 5.5.

See also QSslPreSharedKeyAuthenticator.

[signal] void QNetworkAccessManager::proxyAuthenticationRequired(const QNetworkProxy &proxy, QAuthenticator *authenticator)

This signal is emitted whenever a proxy requests authentication and QNetworkAccessManager cannot find a valid, cached credential. The slot connected to this signal should fill in the credentials for the proxy proxy in the authenticator object.

QNetworkAccessManager will cache the credentials internally. The next time the proxy requests authentication, QNetworkAccessManager will automatically send the same credential without emitting the proxyAuthenticationRequired signal again.

If the proxy rejects the credentials, QNetworkAccessManager will emit the signal again.

See also proxy(), setProxy(), and authenticationRequired().

[signal] void QNetworkAccessManager::sslErrors(QNetworkReply *reply, const QList<QSslError> &errors)

This signal is emitted if the SSL/TLS session encountered errors during the set up, including certificate verification errors. The errors parameter contains the list of errors and reply is the QNetworkReply that is encountering these errors.

To indicate that the errors are not fatal and that the connection should proceed, the QNetworkReply::ignoreSslErrors() function should be called from the slot connected to this signal. If it is not called, the SSL session will be torn down before any data is exchanged (including the URL).

This signal can be used to display an error message to the user indicating that security may be compromised and display the SSL settings (see sslConfiguration() to obtain it). If the user decides to proceed after analyzing the remote certificate, the slot should call ignoreSslErrors().

See also QSslSocket::sslErrors(), QNetworkReply::sslErrors(), QNetworkReply::sslConfiguration(), and QNetworkReply::ignoreSslErrors().

[virtual] QNetworkAccessManager::~QNetworkAccessManager()

Destroys the QNetworkAccessManager object and frees up any resources. Note that QNetworkReply objects that are returned from this class have this object set as their parents, which means that they will be deleted along with it if you don't call QObject::setParent() on them.

[since 5.9] void QNetworkAccessManager::addStrictTransportSecurityHosts(const QList<QHstsPolicy> &knownHosts)

Adds HTTP Strict Transport Security policies into HSTS cache. knownHosts contains the known hosts that have QHstsPolicy information.

Note: An expired policy will remove a known host from the cache, if previously present.

Note: While processing HTTP responses, QNetworkAccessManager can also update the HSTS cache, removing or updating exitsting policies or introducing new knownHosts. The current implementation thus is server-driven, client code can provide QNetworkAccessManager with previously known or discovered policies, but this information can be overridden by "Strict-Transport-Security" response headers.

This function was introduced in Qt 5.9.

See also addStrictTransportSecurityHosts(), enableStrictTransportSecurityStore(), and QHstsPolicy.

[since 5.14] bool QNetworkAccessManager::autoDeleteReplies() const

Returns the true if QNetworkAccessManager is currently configured to automatically delete QNetworkReplies, false otherwise.

This function was introduced in Qt 5.14.

See also setAutoDeleteReplies and QNetworkRequest::AutoDeleteReplyOnFinishAttribute.

QAbstractNetworkCache *QNetworkAccessManager::cache() const

Returns the cache that is used to store data obtained from the network.

See also setCache().

[since 5.0] void QNetworkAccessManager::clearAccessCache()

Flushes the internal cache of authentication data and network connections.

This function is useful for doing auto tests.

This function was introduced in Qt 5.0.

See also clearConnectionCache().

[since 5.9] void QNetworkAccessManager::clearConnectionCache()

Flushes the internal cache of network connections. In contrast to clearAccessCache() the authentication data is preserved.

This function was introduced in Qt 5.9.

See also clearAccessCache().

[since 5.2] void QNetworkAccessManager::connectToHost(const QString &hostName, quint16 port = 80)

Initiates a connection to the host given by hostName at port port. This function is useful to complete the TCP handshake to a host before the HTTP request is made, resulting in a lower network latency.

Note: This function has no possibility to report errors.

This function was introduced in Qt 5.2.

See also connectToHostEncrypted(), get(), post(), put(), and deleteResource().

[since 5.2] void QNetworkAccessManager::connectToHostEncrypted(const QString &hostName, quint16 port = 443, const QSslConfiguration &sslConfiguration = QSslConfiguration::defaultConfiguration())

Initiates a connection to the host given by hostName at port port, using sslConfiguration. This function is useful to complete the TCP and SSL handshake to a host before the HTTPS request is made, resulting in a lower network latency.

Note: Preconnecting a HTTP/2 connection can be done by calling setAllowedNextProtocols() on sslConfiguration with QSslConfiguration::ALPNProtocolHTTP2 contained in the list of allowed protocols. When using HTTP/2, one single connection per host is enough, i.e. calling this method multiple times per host will not result in faster network transactions.

Note: This function has no possibility to report errors.

This function was introduced in Qt 5.2.

See also connectToHost(), get(), post(), put(), and deleteResource().

[since 5.13] void QNetworkAccessManager::connectToHostEncrypted(const QString &hostName, quint16 port, const QSslConfiguration &sslConfiguration, const QString &peerName)

This is an overloaded function.

Initiates a connection to the host given by hostName at port port, using sslConfiguration with peerName set to be the hostName used for certificate validation. This function is useful to complete the TCP and SSL handshake to a host before the HTTPS request is made, resulting in a lower network latency.

Note: Preconnecting a HTTP/2 connection can be done by calling setAllowedNextProtocols() on sslConfiguration with QSslConfiguration::ALPNProtocolHTTP2 contained in the list of allowed protocols. When using HTTP/2, one single connection per host is enough, i.e. calling this method multiple times per host will not result in faster network transactions.

Note: This function has no possibility to report errors.

This function was introduced in Qt 5.13.

See also connectToHost(), get(), post(), put(), and deleteResource().

QNetworkCookieJar *QNetworkAccessManager::cookieJar() const

Returns the QNetworkCookieJar that is used to store cookies obtained from the network as well as cookies that are about to be sent.

See also setCookieJar().

[virtual protected] QNetworkReply *QNetworkAccessManager::createRequest(QNetworkAccessManager::Operation op, const QNetworkRequest &originalReq, QIODevice *outgoingData = nullptr)

Returns a new QNetworkReply object to handle the operation op and request originalReq. The device outgoingData is always 0 for Get and Head requests, but is the value passed to post() and put() in those operations (the QByteArray variants will pass a QBuffer object).

The default implementation calls QNetworkCookieJar::cookiesForUrl() on the cookie jar set with setCookieJar() to obtain the cookies to be sent to the remote server.

The returned object must be in an open state.

QNetworkReply *QNetworkAccessManager::deleteResource(const QNetworkRequest &request)

Sends a request to delete the resource identified by the URL of request.

Note: This feature is currently available for HTTP only, performing an HTTP DELETE request.

See also get(), post(), put(), and sendCustomRequest().

[since 5.10] void QNetworkAccessManager::enableStrictTransportSecurityStore(bool enabled, const QString &storeDir = QString())

If enabled is true, the internal HSTS cache will use a persistent store to read and write HSTS policies. storeDir defines where this store will be located. The default location is defined by QStandardPaths::CacheLocation. If there is no writable QStandartPaths::CacheLocation and storeDir is an empty string, the store will be located in the program's working directory.

Note: If HSTS cache already contains HSTS policies by the time persistent store is enabled, these policies will be preserved in the store. In case both cache and store contain the same known hosts, policies from cache are considered to be more up-to-date (and thus will overwrite the previous values in the store). If this behavior is undesired, enable HSTS store before enabling Strict Tranport Security. By default, the persistent store of HSTS policies is disabled.

This function was introduced in Qt 5.10.

See also isStrictTransportSecurityStoreEnabled(), setStrictTransportSecurityEnabled(), and QStandardPaths::standardLocations().

QNetworkReply *QNetworkAccessManager::get(const QNetworkRequest &request)

Posts a request to obtain the contents of the target request and returns a new QNetworkReply object opened for reading which emits the readyRead() signal whenever new data arrives.

The contents as well as associated headers will be downloaded.

See also post(), put(), deleteResource(), and sendCustomRequest().

QNetworkReply *QNetworkAccessManager::head(const QNetworkRequest &request)

Posts a request to obtain the network headers for request and returns a new QNetworkReply object which will contain such headers.

The function is named after the HTTP request associated (HEAD).

[since 5.9] bool QNetworkAccessManager::isStrictTransportSecurityEnabled() const

Returns true if HTTP Strict Transport Security (HSTS) was enabled. By default HSTS is disabled.

This function was introduced in Qt 5.9.

See also setStrictTransportSecurityEnabled().

[since 5.10] bool QNetworkAccessManager::isStrictTransportSecurityStoreEnabled() const

Returns true if HSTS cache uses a permanent store to load and store HSTS policies.

This function was introduced in Qt 5.10.

See also enableStrictTransportSecurityStore().

QNetworkReply *QNetworkAccessManager::post(const QNetworkRequest &request, QIODevice *data)

Sends an HTTP POST request to the destination specified by request and returns a new QNetworkReply object opened for reading that will contain the reply sent by the server. The contents of the data device will be uploaded to the server.

data must be open for reading and must remain valid until the finished() signal is emitted for this reply.

Note: Sending a POST request on protocols other than HTTP and HTTPS is undefined and will probably fail.

See also get(), put(), deleteResource(), and sendCustomRequest().

QNetworkReply *QNetworkAccessManager::post(const QNetworkRequest &request, const QByteArray &data)

This is an overloaded function.

Sends the contents of the data byte array to the destination specified by request.

QNetworkReply *QNetworkAccessManager::post(const QNetworkRequest &request, QHttpMultiPart *multiPart)

This is an overloaded function.

Sends the contents of the multiPart message to the destination specified by request.

This can be used for sending MIME multipart messages over HTTP.

See also QHttpMultiPart, QHttpPart, and put().

QNetworkProxy QNetworkAccessManager::proxy() const

Returns the QNetworkProxy that the requests sent using this QNetworkAccessManager object will use. The default value for the proxy is QNetworkProxy::DefaultProxy.

See also setProxy(), setProxyFactory(), and proxyAuthenticationRequired().

QNetworkProxyFactory *QNetworkAccessManager::proxyFactory() const

Returns the proxy factory that this QNetworkAccessManager object is using to determine the proxies to be used for requests.

Note that the pointer returned by this function is managed by QNetworkAccessManager and could be deleted at any time.

See also setProxyFactory() and proxy().

QNetworkReply *QNetworkAccessManager::put(const QNetworkRequest &request, QIODevice *data)

Uploads the contents of data to the destination request and returns a new QNetworkReply object that will be open for reply.

data must be opened for reading when this function is called and must remain valid until the finished() signal is emitted for this reply.

Whether anything will be available for reading from the returned object is protocol dependent. For HTTP, the server may send a small HTML page indicating the upload was successful (or not). Other protocols will probably have content in their replies.

Note: For HTTP, this request will send a PUT request, which most servers do not allow. Form upload mechanisms, including that of uploading files through HTML forms, use the POST mechanism.

See also get(), post(), deleteResource(), and sendCustomRequest().

QNetworkReply *QNetworkAccessManager::put(const QNetworkRequest &request, const QByteArray &data)

This is an overloaded function.

Sends the contents of the data byte array to the destination specified by request.

QNetworkReply *QNetworkAccessManager::put(const QNetworkRequest &request, QHttpMultiPart *multiPart)

This is an overloaded function.

Sends the contents of the multiPart message to the destination specified by request.

This can be used for sending MIME multipart messages over HTTP.

See also QHttpMultiPart, QHttpPart, and post().

[since 5.9] QNetworkRequest::RedirectPolicy QNetworkAccessManager::redirectPolicy() const

Returns the redirect policy that is used when creating new requests.

This function was introduced in Qt 5.9.

See also setRedirectPolicy() and QNetworkRequest::RedirectPolicy.

QNetworkReply *QNetworkAccessManager::sendCustomRequest(const QNetworkRequest &request, const QByteArray &verb, QIODevice *data = nullptr)

Sends a custom request to the server identified by the URL of request.

It is the user's responsibility to send a verb to the server that is valid according to the HTTP specification.

This method provides means to send verbs other than the common ones provided via get() or post() etc., for instance sending an HTTP OPTIONS command.

If data is not empty, the contents of the data device will be uploaded to the server; in that case, data must be open for reading and must remain valid until the finished() signal is emitted for this reply.

Note: This feature is currently available for HTTP(S) only.

See also get(), post(), put(), and deleteResource().

[since 5.8] QNetworkReply *QNetworkAccessManager::sendCustomRequest(const QNetworkRequest &request, const QByteArray &verb, const QByteArray &data)

This is an overloaded function.

Sends the contents of the data byte array to the destination specified by request.

This function was introduced in Qt 5.8.

[since 5.8] QNetworkReply *QNetworkAccessManager::sendCustomRequest(const QNetworkRequest &request, const QByteArray &verb, QHttpMultiPart *multiPart)

This is an overloaded function.

Sends a custom request to the server identified by the URL of request.

Sends the contents of the multiPart message to the destination specified by request.

This can be used for sending MIME multipart messages for custom verbs.

This function was introduced in Qt 5.8.

See also QHttpMultiPart, QHttpPart, and put().

[since 5.14] void QNetworkAccessManager::setAutoDeleteReplies(bool shouldAutoDelete)

Enables or disables automatic deletion of QNetworkReplies.

Setting shouldAutoDelete to true is the same as setting the QNetworkRequest::AutoDeleteReplyOnFinishAttribute attribute to true on all future QNetworkRequests passed to this instance of QNetworkAccessManager unless the attribute was already explicitly set on the QNetworkRequest.

This function was introduced in Qt 5.14.

See also autoDeleteReplies and QNetworkRequest::AutoDeleteReplyOnFinishAttribute.

void QNetworkAccessManager::setCache(QAbstractNetworkCache *cache)

Sets the manager's network cache to be the cache specified. The cache is used for all requests dispatched by the manager.

Use this function to set the network cache object to a class that implements additional features, like saving the cookies to permanent storage.

Note: QNetworkAccessManager takes ownership of the cache object.

QNetworkAccessManager by default does not have a set cache. Qt provides a simple disk cache, QNetworkDiskCache, which can be used.

See also cache() and QNetworkRequest::CacheLoadControl.

void QNetworkAccessManager::setCookieJar(QNetworkCookieJar *cookieJar)

Sets the manager's cookie jar to be the cookieJar specified. The cookie jar is used by all requests dispatched by the manager.

Use this function to set the cookie jar object to a class that implements additional features, like saving the cookies to permanent storage.

Note: QNetworkAccessManager takes ownership of the cookieJar object.

If cookieJar is in the same thread as this QNetworkAccessManager, it will set the parent of the cookieJar so that the cookie jar is deleted when this object is deleted as well. If you want to share cookie jars between different QNetworkAccessManager objects, you may want to set the cookie jar's parent to 0 after calling this function.

QNetworkAccessManager by default does not implement any cookie policy of its own: it accepts all cookies sent by the server, as long as they are well formed and meet the minimum security requirements (cookie domain matches the request's and cookie path matches the request's). In order to implement your own security policy, override the QNetworkCookieJar::cookiesForUrl() and QNetworkCookieJar::setCookiesFromUrl() virtual functions. Those functions are called by QNetworkAccessManager when it detects a new cookie.

See also cookieJar(), QNetworkCookieJar::cookiesForUrl(), and QNetworkCookieJar::setCookiesFromUrl().

void QNetworkAccessManager::setProxy(const QNetworkProxy &proxy)

Sets the proxy to be used in future requests to be proxy. This does not affect requests that have already been sent. The proxyAuthenticationRequired() signal will be emitted if the proxy requests authentication.

A proxy set with this function will be used for all requests issued by QNetworkAccessManager. In some cases, it might be necessary to select different proxies depending on the type of request being sent or the destination host. If that's the case, you should consider using setProxyFactory().

See also proxy() and proxyAuthenticationRequired().

void QNetworkAccessManager::setProxyFactory(QNetworkProxyFactory *factory)

Sets the proxy factory for this class to be factory. A proxy factory is used to determine a more specific list of proxies to be used for a given request, instead of trying to use the same proxy value for all requests.

All queries sent by QNetworkAccessManager will have type QNetworkProxyQuery::UrlRequest.

For example, a proxy factory could apply the following rules:

• if the target address is in the local network (for example, if the hostname contains no dots or if it's an IP address in the organization's range), return QNetworkProxy::NoProxy
• if the request is FTP, return an FTP proxy
• if the request is HTTP or HTTPS, then return an HTTP proxy
• otherwise, return a SOCKSv5 proxy server

The lifetime of the object factory will be managed by QNetworkAccessManager. It will delete the object when necessary.

Note: If a specific proxy is set with setProxy(), the factory will not be used.

See also proxyFactory(), setProxy(), and QNetworkProxyQuery.

[since 5.9] void QNetworkAccessManager::setRedirectPolicy(QNetworkRequest::RedirectPolicy policy)

Sets the manager's redirect policy to be the policy specified. This policy will affect all subsequent requests created by the manager.

Use this function to enable or disable HTTP redirects on the manager's level.

Note: When creating a request QNetworkRequest::RedirectAttributePolicy has the highest priority, next by priority the manager's policy.

The default value is QNetworkRequest::NoLessSafeRedirectPolicy. Clients relying on manual redirect handling are encouraged to set this policy explicitly in their code.

This function was introduced in Qt 5.9.

See also redirectPolicy() and QNetworkRequest::RedirectPolicy.

[since 5.9] void QNetworkAccessManager::setStrictTransportSecurityEnabled(bool enabled)

If enabled is true, QNetworkAccessManager follows the HTTP Strict Transport Security policy (HSTS, RFC6797). When processing a request, QNetworkAccessManager automatically replaces the "http" scheme with "https" and uses a secure transport for HSTS hosts. If it's set explicitly, port 80 is replaced by port 443.

When HSTS is enabled, for each HTTP response containing HSTS header and received over a secure transport, QNetworkAccessManager will update its HSTS cache, either remembering a host with a valid policy or removing a host with an expired or disabled HSTS policy.

This function was introduced in Qt 5.9.

See also isStrictTransportSecurityEnabled().

[since 5.15] void QNetworkAccessManager::setTransferTimeout(int timeout = QNetworkRequest::DefaultTransferTimeoutConstant)

Sets timeout as the transfer timeout in milliseconds.

Transfers are aborted if no bytes are transferred before the timeout expires. Zero means no timer is set. If no argument is provided, the timeout is QNetworkRequest::DefaultTransferTimeoutConstant. If this function is not called, the timeout is disabled and has the value zero. The request-specific non-zero timeouts set for the requests that are executed override this value. This means that if QNetworkAccessManager has an enabled timeout, it needs to be disabled to execute a request without a timeout.

This function was introduced in Qt 5.15.

See also transferTimeout().

[since 5.9] QList<QHstsPolicy> QNetworkAccessManager::strictTransportSecurityHosts() const

Returns the list of HTTP Strict Transport Security policies. This list can differ from what was initially set via addStrictTransportSecurityHosts() if HSTS cache was updated from a "Strict-Transport-Security" response header.

This function was introduced in Qt 5.9.

See also addStrictTransportSecurityHosts() and QHstsPolicy.

[virtual, since 5.2] QStringList QNetworkAccessManager::supportedSchemes() const

Lists all the URL schemes supported by the access manager.

Reimplement this method to provide your own supported schemes in a QNetworkAccessManager subclass. It is for instance necessary when your subclass provides support for new protocols.

This function was introduced in Qt 5.2.

[since 5.15] int QNetworkAccessManager::transferTimeout() const

Returns the timeout used for transfers, in milliseconds.

This timeout is zero if setTransferTimeout() hasn't been called, which means that the timeout is not used.

This function was introduced in Qt 5.15.

See also setTransferTimeout().