These classes are used to handle input and output to and from external devices, processes, files etc. as well as manipulating files and directories.
| QAbstractFileEngine | The QAbstractFileEngine class provides an abstraction for accessing the filesystem. |
| QAbstractFileEngineHandler | The QAbstractFileEngineHandler class provides a way to register custom file engines with your application. |
| QAbstractSocket | The QAbstractSocket class provides the base functionality common to all socket types. |
| QAuthenticator | The QAuthenticator class provides an authentication object. |
| QBuffer | The QBuffer class provides a QIODevice interface for a QByteArray. |
| QClipboard | The QClipboard class provides access to the window system clipboard. |
| QDataStream | The QDataStream class provides serialization of binary data to a QIODevice. |
| QDir | The QDir class provides access to directory structures and their contents. |
| QFile | The QFile class provides an interface for reading from and writing to files. |
| QFileInfo | The QFileInfo class provides system-independent file information. |
| QFileSystemWatcher | The QFileSystemWatcher class provides an interface for monitoring files and directories for modifications. |
| QFtp | The QFtp class provides an implementation of the client side of FTP protocol. |
| QHostAddress | The QHostAddress class provides an IP address. |
| QHostInfo | The QHostInfo class provides static functions for host name lookups. |
| QHttp | The QHttp class provides an implementation of the HTTP protocol. |
| QHttpHeader | The QHttpHeader class contains header information for HTTP. |
| QHttpRequestHeader | The QHttpRequestHeader class contains request header information for HTTP. |
| QHttpResponseHeader | The QHttpResponseHeader class contains response header information for HTTP. |
| QIODevice | The QIODevice class is the base interface class of all I/O devices in Qt. |
| QImageReader | The QImageReader class provides a format independent interface for reading images from files or other devices. |
| QImageWriter | The QImageWriter class provides a format independent interface for writing images to files or other devices. |
| QMacPasteboardMime | The QMacPasteboardMime class maps open-standard MIME to Mac flavors. |
| QNetworkAddressEntry | The QNetworkAddressEntry class stores one IP address supported by a network interface, along with its associated netmask and broadcast address. |
| QNetworkInterface | The QNetworkInterface class provides a listing of the host's IP addresses and network interfaces. |
| QNetworkProxy | The QNetworkProxy class provides a network layer proxy. |
| QPictureIO | The QPictureIO class contains parameters for loading and saving pictures. |
| QProcess | The QProcess class is used to start external programs and to communicate with them. |
| QResource | The QResource class provides an interface for reading directly from resources. |
| QSettings | The QSettings class provides persistent platform-independent application settings. |
| QSignalMapper | The QSignalMapper class bundles signals from identifiable senders. |
| QSocketNotifier | The QSocketNotifier class provides support for monitoring activity on a file descriptor. |
| QSslCertificate | The QSslCertificate class provides a convenient API for an X509 certificate. |
| QSslCipher | The QSslCipher class represents an SSL cryptographic cipher. |
| QSslError | The QSslError class provides an SSL error. |
| QSslKey | The QSslKey class provides an interface for private and public keys. |
| QSslSocket | The QSslSocket class provides an SSL encrypted socket for both clients and servers. |
| QTcpServer | The QTcpServer class provides a TCP-based server. |
| QTcpSocket | The QTcpSocket class provides a TCP socket. |
| QTemporaryFile | The QTemporaryFile class is an I/O device that operates on temporary files. |
| QTextIStream | The QTextIStream class is a convenience class for input streams. |
| QTextOStream | The QTextOStream class is a convenience class for output streams. |
| QTextStream | The QTextStream class provides a convenient interface for reading and writing text. |
| QUdpSocket | The QUdpSocket class provides a UDP socket. |
| QUrl | The QUrl class provides a convenient interface for working with URLs. |
| QUrlInfo | The QUrlInfo class stores information about URLs. |
| QWindowsMime | The QWindowsMime class maps open-standard MIME to Window Clipboard formats. |