QNetworkReply Class

The QNetworkReply class contains the data and headers for a request sent with QNetworkAccessManager. More...

Header: #include <QNetworkReply>
CMake: find_package(Qt6 REQUIRED COMPONENTS Network)
target_link_libraries(mytarget PRIVATE Qt6::Network)
qmake: QT += network
Inherits: QIODevice

Note: All functions in this class are reentrant.

Public Types

enum NetworkError { NoError, ConnectionRefusedError, RemoteHostClosedError, HostNotFoundError, TimeoutError, …, UnknownServerError }

Public Functions

virtual ~QNetworkReply()
QVariant attribute(QNetworkRequest::Attribute code) const
QNetworkReply::NetworkError error() const
bool hasRawHeader(QAnyStringView headerName) const
QVariant header(QNetworkRequest::KnownHeaders header) const
void ignoreSslErrors(const QList<QSslError> &errors)
bool isFinished() const
bool isRunning() const
QNetworkAccessManager *manager() const
QNetworkAccessManager::Operation operation() const
QByteArray rawHeader(QAnyStringView headerName) const
QList<QByteArray> rawHeaderList() const
const QList<QNetworkReply::RawHeaderPair> &rawHeaderPairs() const
qint64 readBufferSize() const
QNetworkRequest request() const
virtual void setReadBufferSize(qint64 size)
void setSslConfiguration(const QSslConfiguration &config)
QSslConfiguration sslConfiguration() const
QUrl url() const

Reimplemented Public Functions

virtual void close() override

Public Slots

virtual void abort() = 0
virtual void ignoreSslErrors()


void downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
void encrypted()
void errorOccurred(QNetworkReply::NetworkError code)
void finished()
void metaDataChanged()
void preSharedKeyAuthenticationRequired(QSslPreSharedKeyAuthenticator *authenticator)
void redirectAllowed()
void redirected(const QUrl &url)
(since 6.3) void requestSent()
(since 6.3) void socketStartedConnecting()
void sslErrors(const QList<QSslError> &errors)
void uploadProgress(qint64 bytesSent, qint64 bytesTotal)

Protected Functions

QNetworkReply(QObject *parent = nullptr)
virtual void ignoreSslErrorsImplementation(const QList<QSslError> &errors)
void setAttribute(QNetworkRequest::Attribute code, const QVariant &value)
void setError(QNetworkReply::NetworkError errorCode, const QString &errorString)
void setFinished(bool finished)
void setHeader(QNetworkRequest::KnownHeaders header, const QVariant &value)
void setOperation(QNetworkAccessManager::Operation operation)
void setRawHeader(const QByteArray &headerName, const QByteArray &value)
void setRequest(const QNetworkRequest &request)
virtual void setSslConfigurationImplementation(const QSslConfiguration &configuration)
void setUrl(const QUrl &url)
virtual void sslConfigurationImplementation(QSslConfiguration &configuration) const

Detailed Description

The QNetworkReply class contains the data and meta data related to a request posted with QNetworkAccessManager. Like QNetworkRequest, it contains a URL and headers (both in parsed and raw form), some information about the reply's state and the contents of the reply itself.

QNetworkReply is a sequential-access QIODevice, which means that once data is read from the object, it is no longer kept by the device. It is therefore the application's responsibility to keep this data if it needs to. Whenever more data is received from the network and processed, the readyRead() signal is emitted.

The downloadProgress() signal is also emitted when data is received, but the number of bytes contained in it may not represent the actual bytes received, if any transformation is done to the contents (for example, decompressing and removing the protocol overhead).

Even though QNetworkReply is a QIODevice connected to the contents of the reply, it also emits the uploadProgress() signal, which indicates the progress of the upload for operations that have such content.

Note: Do not delete the object in the slot connected to the errorOccurred() or finished() signal. Use deleteLater().

See also QNetworkRequest and QNetworkAccessManager.

Member Type Documentation

enum QNetworkReply::NetworkError

Indicates all possible error conditions found during the processing of the request.

QNetworkReply::NoError0no error condition.

Note: When the HTTP protocol returns a redirect no error will be reported. You can check if there is a redirect with the QNetworkRequest::RedirectionTargetAttribute attribute.

QNetworkReply::ConnectionRefusedError1the remote server refused the connection (the server is not accepting requests)
QNetworkReply::RemoteHostClosedError2the remote server closed the connection prematurely, before the entire reply was received and processed
QNetworkReply::HostNotFoundError3the remote host name was not found (invalid hostname)
QNetworkReply::TimeoutError4the connection to the remote server timed out
QNetworkReply::OperationCanceledError5the operation was canceled via calls to abort() or close() before it was finished.
QNetworkReply::SslHandshakeFailedError6the SSL/TLS handshake failed and the encrypted channel could not be established. The sslErrors() signal should have been emitted.
QNetworkReply::TemporaryNetworkFailureError7the connection was broken due to disconnection from the network, however the system has initiated roaming to another access point. The request should be resubmitted and will be processed as soon as the connection is re-established.
QNetworkReply::NetworkSessionFailedError8the connection was broken due to disconnection from the network or failure to start the network.
QNetworkReply::BackgroundRequestNotAllowedError9the background request is not currently allowed due to platform policy.
QNetworkReply::TooManyRedirectsError10while following redirects, the maximum limit was reached. The limit is by default set to 50 or as set by QNetworkRequest::setMaxRedirectsAllowed(). (This value was introduced in 5.6.)
QNetworkReply::InsecureRedirectError11while following redirects, the network access API detected a redirect from a encrypted protocol (https) to an unencrypted one (http). (This value was introduced in 5.6.)
QNetworkReply::ProxyConnectionRefusedError101the connection to the proxy server was refused (the proxy server is not accepting requests)
QNetworkReply::ProxyConnectionClosedError102the proxy server closed the connection prematurely, before the entire reply was received and processed
QNetworkReply::ProxyNotFoundError103the proxy host name was not found (invalid proxy hostname)
QNetworkReply::ProxyTimeoutError104the connection to the proxy timed out or the proxy did not reply in time to the request sent
QNetworkReply::ProxyAuthenticationRequiredError105the proxy requires authentication in order to honour the request but did not accept any credentials offered (if any)
QNetworkReply::ContentAccessDenied201the access to the remote content was denied (similar to HTTP error 403)
QNetworkReply::ContentOperationNotPermittedError202the operation requested on the remote content is not permitted
QNetworkReply::ContentNotFoundError203the remote content was not found at the server (similar to HTTP error 404)
QNetworkReply::AuthenticationRequiredError204the remote server requires authentication to serve the content but the credentials provided were not accepted (if any)
QNetworkReply::ContentReSendError205the request needed to be sent again, but this failed for example because the upload data could not be read a second time.
QNetworkReply::ContentConflictError206the request could not be completed due to a conflict with the current state of the resource.
QNetworkReply::ContentGoneError207the requested resource is no longer available at the server.
QNetworkReply::InternalServerError401the server encountered an unexpected condition which prevented it from fulfilling the request.
QNetworkReply::OperationNotImplementedError402the server does not support the functionality required to fulfill the request.
QNetworkReply::ServiceUnavailableError403the server is unable to handle the request at this time.
QNetworkReply::ProtocolUnknownError301the Network Access API cannot honor the request because the protocol is not known
QNetworkReply::ProtocolInvalidOperationError302the requested operation is invalid for this protocol
QNetworkReply::UnknownNetworkError99an unknown network-related error was detected
QNetworkReply::UnknownProxyError199an unknown proxy-related error was detected
QNetworkReply::UnknownContentError299an unknown error related to the remote content was detected
QNetworkReply::ProtocolFailure399a breakdown in protocol was detected (parsing error, invalid or unexpected responses, etc.)
QNetworkReply::UnknownServerError499an unknown error related to the server response was detected

See also error() and errorOccurred().


RawHeaderPair is a QPair<QByteArray, QByteArray> where the first QByteArray is the header name and the second is the header.

Member Function Documentation

[explicit protected] QNetworkReply::QNetworkReply(QObject *parent = nullptr)

Creates a QNetworkReply object with parent parent.

You cannot directly instantiate QNetworkReply objects. Use QNetworkAccessManager functions to do that.

[virtual noexcept] QNetworkReply::~QNetworkReply()

Disposes of this reply and frees any resources associated with it. If any network connections are still open, they will be closed.

See also abort() and close().

[pure virtual slot] void QNetworkReply::abort()

Aborts the operation immediately and close down any network connections still open. Uploads still in progress are also aborted.

The finished() signal will also be emitted.

See also close() and finished().

QVariant QNetworkReply::attribute(QNetworkRequest::Attribute code) const

Returns the attribute associated with the code code. If the attribute has not been set, it returns an invalid QVariant (type QMetaType::UnknownType).

You can expect the default values listed in QNetworkRequest::Attribute to be applied to the values returned by this function.

See also setAttribute() and QNetworkRequest::Attribute.

[override virtual] void QNetworkReply::close()

Reimplements: QIODevice::close().

Closes this device for reading. Unread data is discarded, but the network resources are not discarded until they are finished. In particular, if any upload is in progress, it will continue until it is done.

The finished() signal is emitted when all operations are over and the network resources are freed.

See also abort() and finished().

[signal] void QNetworkReply::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)

This signal is emitted to indicate the progress of the download part of this network request, if there's any. If there's no download associated with this request, this signal will be emitted once with 0 as the value of both bytesReceived and bytesTotal.

The bytesReceived parameter indicates the number of bytes received, while bytesTotal indicates the total number of bytes expected to be downloaded. If the number of bytes to be downloaded is not known, bytesTotal will be -1.

The download is finished when bytesReceived is equal to bytesTotal. At that time, bytesTotal will not be -1.

Note that the values of both bytesReceived and bytesTotal may be different from size(), the total number of bytes obtained through read() or readAll(), or the value of the header(ContentLengthHeader). The reason for that is that there may be protocol overhead or the data may be compressed during the download.

See also uploadProgress() and bytesAvailable().

[signal] void QNetworkReply::encrypted()

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. 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.

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

QNetworkReply::NetworkError QNetworkReply::error() const

Returns the error that was found during the processing of this request. If no error was found, returns NoError.

See also setError().

[signal] void QNetworkReply::errorOccurred(QNetworkReply::NetworkError code)

This signal is emitted when the reply detects an error in processing. The finished() signal will probably follow, indicating that the connection is over.

The code parameter contains the code of the error that was detected. Call errorString() to obtain a textual representation of the error condition.

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

See also error() and errorString().

[signal] void QNetworkReply::finished()

This signal is emitted when the reply has finished processing. After this signal is emitted, there will be no more updates to the reply's data or metadata.

Unless close() or abort() have been called, the reply will still be opened for reading, so the data can be retrieved by calls to read() or readAll(). In particular, if no calls to read() were made as a result of readyRead(), a call to readAll() will retrieve the full contents in a QByteArray.

This signal is emitted in tandem with QNetworkAccessManager::finished() where that signal's reply parameter is this object.

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

You can also use isFinished() to check if a QNetworkReply has finished even before you receive the finished() signal.

See also setFinished(), QNetworkAccessManager::finished(), and isFinished().

bool QNetworkReply::hasRawHeader(QAnyStringView headerName) const

Returns true if the raw header of name headerName was sent by the remote server

Note: In Qt versions prior to 6.7, this function took QByteArray only.

See also rawHeader().

Returns the value of the known header header, if that header was sent by the remote server. If the header was not sent, returns an invalid QVariant.

See also rawHeader(), setHeader(), and QNetworkRequest::header().

[virtual slot] void QNetworkReply::ignoreSslErrors()

If this function is called, SSL errors related to network connection will be ignored, including certificate validation errors.

Warning: Be sure to always let the user inspect the errors reported by the sslErrors() signal, and only call this method upon confirmation from the user that proceeding is ok. If there are unexpected errors, the reply should be aborted. Calling this method without inspecting the actual errors will most likely pose a security risk for your application. Use it with great care!

This function can be called from the slot connected to the sslErrors() signal, which indicates which errors were found.

Note: If HTTP Strict Transport Security is enabled for QNetworkAccessManager, this function has no effect.

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

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

This is an overloaded function.

If this function is called, the SSL errors given in errors will be ignored.

Note: Because most SSL errors are associated with a certificate, for most of them you must set the expected certificate this SSL error is related to. If, for instance, you want to issue a request to a server that uses a self-signed certificate, consider the following snippet:

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

QNetworkReply *reply = manager.get(QNetworkRequest(QUrl("https://server.tld/index.html")));
// here connect signals etc.

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.

Note: If HTTP Strict Transport Security is enabled for QNetworkAccessManager, this function has no effect.

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

[virtual protected] void QNetworkReply::ignoreSslErrorsImplementation(const QList<QSslError> &errors)

This virtual method is provided to enable overriding the behavior of ignoreSslErrors(). ignoreSslErrors() is a public wrapper for this method. errors contains the errors the user wishes ignored.

See also ignoreSslErrors().

bool QNetworkReply::isFinished() const

Returns true when the reply has finished or was aborted.

See also isRunning().

bool QNetworkReply::isRunning() const

Returns true when the request is still processing and the reply has not finished or was aborted yet.

See also isFinished().

QNetworkAccessManager *QNetworkReply::manager() const

Returns the QNetworkAccessManager that was used to create this QNetworkReply object. Initially, it is also the parent object.

[signal] void QNetworkReply::metaDataChanged()

This signal is emitted whenever the metadata in this reply changes. metadata is any information that is not the content (data) itself, including the network headers. In the majority of cases, the metadata will be known fully by the time the first byte of data is received. However, it is possible to receive updates of headers or other metadata during the processing of the data.

See also header(), rawHeaderList(), rawHeader(), and hasRawHeader().

QNetworkAccessManager::Operation QNetworkReply::operation() const

Returns the operation that was posted for this reply.

See also setOperation().

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

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.

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.

See also QSslPreSharedKeyAuthenticator.

QByteArray QNetworkReply::rawHeader(QAnyStringView headerName) const

Returns the raw contents of the header headerName as sent by the remote server. If there is no such header, returns an empty byte array, which may be indistinguishable from an empty header. Use hasRawHeader() to verify if the server sent such header field.

Note: In Qt versions prior to 6.7, this function took QByteArray only.

See also setRawHeader(), hasRawHeader(), and header().

QList<QByteArray> QNetworkReply::rawHeaderList() const

Returns a list of headers fields that were sent by the remote server, in the order that they were sent. Duplicate headers are merged together and take place of the latter duplicate.

const QList<QNetworkReply::RawHeaderPair> &QNetworkReply::rawHeaderPairs() const

Returns a list of raw header pairs.

qint64 QNetworkReply::readBufferSize() const

Returns the size of the read buffer, in bytes.

See also setReadBufferSize().

[signal] void QNetworkReply::redirectAllowed()

When client code handling the redirected() signal has verified the new URL, it emits this signal to allow the redirect to go ahead. This protocol applies to network requests whose redirects policy is set to QNetworkRequest::UserVerifiedRedirectPolicy

See also QNetworkRequest::UserVerifiedRedirectPolicy, QNetworkAccessManager::setRedirectPolicy(), and QNetworkRequest::RedirectPolicyAttribute.

[signal] void QNetworkReply::redirected(const QUrl &url)

This signal is emitted if the QNetworkRequest::ManualRedirectPolicy was not set in the request and the server responded with a 3xx status (specifically 301, 302, 303, 305, 307 or 308 status code) with a valid url in the location header, indicating a HTTP redirect. The url parameter contains the new redirect url as returned by the server in the location header.

See also QNetworkRequest::RedirectPolicy.

QNetworkRequest QNetworkReply::request() const

Returns the request that was posted for this reply. In special, note that the URL for the request may be different than that of the reply.

See also QNetworkRequest::url(), url(), and setRequest().

[signal, since 6.3] void QNetworkReply::requestSent()

This signal is emitted 1 or more times when the request was sent. Useful for custom progress or timeout handling.

This function was introduced in Qt 6.3.

See also metaDataChanged() and socketStartedConnecting().

[protected] void QNetworkReply::setAttribute(QNetworkRequest::Attribute code, const QVariant &value)

Sets the attribute code to have value value. If code was previously set, it will be overridden. If value is an invalid QVariant, the attribute will be unset.

See also attribute() and QNetworkRequest::setAttribute().

[protected] void QNetworkReply::setError(QNetworkReply::NetworkError errorCode, const QString &errorString)

Sets the error condition to be errorCode. The human-readable message is set with errorString.

Calling setError() does not emit the errorOccurred(QNetworkReply::NetworkError) signal.

See also error() and errorString().

[protected] void QNetworkReply::setFinished(bool finished)

Sets the reply as finished.

After having this set the replies data must not change.

See also finished() and isFinished().

[protected] void QNetworkReply::setHeader(QNetworkRequest::KnownHeaders header, const QVariant &value)

Sets the known header header to be of value value. The corresponding raw form of the header will be set as well.

See also header(), setRawHeader(), and QNetworkRequest::setHeader().

[protected] void QNetworkReply::setOperation(QNetworkAccessManager::Operation operation)

Sets the associated operation for this object to be operation. This value will be returned by operation().

Note: The operation should be set when this object is created and not changed again.

See also operation() and setRequest().

[protected] void QNetworkReply::setRawHeader(const QByteArray &headerName, const QByteArray &value)

Sets the raw header headerName to be of value value. If headerName was previously set, it is overridden. Multiple HTTP headers of the same name are functionally equivalent to one single header with the values concatenated, separated by commas.

If headerName matches a known header, the value value will be parsed and the corresponding parsed form will also be set.

See also rawHeader(), header(), setHeader(), and QNetworkRequest::setRawHeader().

[virtual] void QNetworkReply::setReadBufferSize(qint64 size)

Sets the size of the read buffer to be size bytes. The read buffer is the buffer that holds data that is being downloaded off the network, before it is read with QIODevice::read(). Setting the buffer size to 0 will make the buffer unlimited in size.

QNetworkReply will try to stop reading from the network once this buffer is full (i.e., bytesAvailable() returns size or more), thus causing the download to throttle down as well. If the buffer is not limited in size, QNetworkReply will try to download as fast as possible from the network.

Unlike QAbstractSocket::setReadBufferSize(), QNetworkReply cannot guarantee precision in the read buffer size. That is, bytesAvailable() can return more than size.

See also readBufferSize().

[protected] void QNetworkReply::setRequest(const QNetworkRequest &request)

Sets the associated request for this object to be request. This value will be returned by request().

Note: The request should be set when this object is created and not changed again.

See also request() and setOperation().

void QNetworkReply::setSslConfiguration(const QSslConfiguration &config)

Sets the SSL configuration for the network connection associated with this request, if possible, to be that of config.

See also sslConfiguration().

[virtual protected] void QNetworkReply::setSslConfigurationImplementation(const QSslConfiguration &configuration)

This virtual method is provided to enable overriding the behavior of setSslConfiguration(). setSslConfiguration() is a public wrapper for this method. If you override this method use configuration to set the SSL configuration.

See also sslConfigurationImplementation() and setSslConfiguration().

[protected] void QNetworkReply::setUrl(const QUrl &url)

Sets the URL being processed to be url. Normally, the URL matches that of the request that was posted, but for a variety of reasons it can be different (for example, a file path being made absolute or canonical).

See also url(), request(), and QNetworkRequest::url().

[signal, since 6.3] void QNetworkReply::socketStartedConnecting()

This signal is emitted 0 or more times, when the socket is connecting, before sending the request. Useful for custom progress or timeout handling.

This function was introduced in Qt 6.3.

See also metaDataChanged() and requestSent().

QSslConfiguration QNetworkReply::sslConfiguration() const

Returns the SSL configuration and state associated with this reply, if SSL was used. It will contain the remote server's certificate, its certificate chain leading to the Certificate Authority as well as the encryption ciphers in use.

The peer's certificate and its certificate chain will be known by the time sslErrors() is emitted, if it's emitted.

See also setSslConfiguration().

[virtual protected] void QNetworkReply::sslConfigurationImplementation(QSslConfiguration &configuration) const

This virtual method is provided to enable overriding the behavior of sslConfiguration(). sslConfiguration() is a public wrapper for this method. The configuration will be returned in configuration.

See also setSslConfigurationImplementation() and sslConfiguration().

[signal] void QNetworkReply::sslErrors(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.

To indicate that the errors are not fatal and that the connection should proceed, the 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(), QNetworkAccessManager::sslErrors(), sslConfiguration(), and ignoreSslErrors().

[signal] void QNetworkReply::uploadProgress(qint64 bytesSent, qint64 bytesTotal)

This signal is emitted to indicate the progress of the upload part of this network request, if there's any. If there's no upload associated with this request, this signal will not be emitted.

The bytesSent parameter indicates the number of bytes uploaded, while bytesTotal indicates the total number of bytes to be uploaded. If the number of bytes to be uploaded could not be determined, bytesTotal will be -1.

The upload is finished when bytesSent is equal to bytesTotal. At that time, bytesTotal will not be -1.

See also downloadProgress().

QUrl QNetworkReply::url() const

Returns the URL of the content downloaded or uploaded. Note that the URL may be different from that of the original request. If redirections were enabled in the request, then this function returns the current url that the network API is accessing, i.e the url of the resource the request got redirected to.

See also request(), setUrl(), QNetworkRequest::url(), and redirected().

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