QNetworkReply

QNetworkReply is a class in the Qt Network module that represents the reply to a network request. It is produced by QNetworkAccessManager when performing an operation such as GET, POST, or others. The reply encapsulates the response data as well as metadata such as HTTP headers, status codes, and the request URL.

The reply object is created as part of the lifecycle of a network operation and is typically consumed by the application after the corresponding request is issued. It inherits from QObject and QIODevice, allowing event-driven data handling. Common signals include readyRead() to indicate that new data can be read, finished() when the operation completes, and error signals to report failures. The specific error reporting is exposed via error() or errorString(), depending on the Qt version and API usage.

Data access is provided through the streaming interface of QIODevice. You can read the response payload incrementally with readData(), or retrieve the entire content with readAll(). Important convenience methods include bytesAvailable() and isSequential(), which help callers manage data flow. A consumer typically connects to readyRead() and reads data as it becomes available.

Metadata and headers are accessible through various helpers. The reply exposes the original URL via url() and the operation type via operation(). Response headers can be queried with header(QNetworkRequest::KnownHeaders) and rawHeaderPairs(), providing both known and raw header information. Attributes such as the HTTP status code and reason phrase are obtainable via attribute(), using known attributes like HttpStatusCodeAttribute.

Error handling and cancellation are supported through abort() to cancel an in-progress request and error reporting mechanisms (NetworkError enum and errorString()). The NetworkError enum covers conditions such as NoError, ConnectionRefusedError, RemoteHostClosedError, TimeoutError, and others. QNetworkReply is intended to be used in conjunction with QNetworkAccessManager and is typically managed by deleting the object after finished, often via deleteLater().