Qt Remote Objects

Remote Object Concepts

Qt Remote Objects (QtRO) is an Inter-Process Communication (IPC) module developed for Qt. This module extends Qt's existing functionalities to enable information exchange between processes or computers, easily.

One of Qt's key features, to enable this information exchange, is the distinction between an object's API (defined by its properties, signals, and slots) and the implementation of that API. QtRO's purpose is to meet that expected API, even if the true QObject is in a different process. A slot called on a copy of an object (the Replica in QtRO) is forwarded to the true object (the Source in QtRO) for handling. Every Replica receives updates to the Source, either property changes or emitted signals.

A Replica is a light-weight proxy for the Source object, but a Replica supports the same connections and behavior of QObjects, which makes it usable in the same way as any other QObject that Qt provides. Behind the scenes, QtRO handles everything that's necessary for the Replica to look like its Source.

Note that Remote Objects behave differently from traditional Remote Procedure Call (RPC) implementations, for example:

  • In RPC, the client makes a request and waits for the response.
  • In RPC, the server doesn't push anything to the client unless it's in response to a request.
  • Often, the design of RPC is such that different clients are independent of each other: for instance, two clients can ask a mapping service for directions and get different results.

While it is possible to implement this RPC-style behavior in QtRO, as Sources without properties, and slots that have return values, QtRO hides the fact that the processing is really remote. You let a node give you the Replica instead of creating it yourself, possibly use the status signals (isReplicaValid()), but then interact with the object like you would with any other QObject-based type.

Get Started

To enable Qt Remote Objects in a project, add this directive into the C++ files:

#include <QtRemoteObjects>

To link against the Qt Remote Objects module, add this line to the project file:

QT += remoteobjects

Guides

Reference

Qt Remote Objects C++ Classes Qt Remote Objects QML Types

Licenses

Qt Remote Objects is available under commercial licenses from The Qt Company. In addition, it is available under the GNU Lesser General Public License, version 3, or the GNU General Public License, version 2. See Qt Licensing for further details.

© 2019 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.