Qt GRPC

Qt GRPC, together with the Qt Protobuf module, enables fast and space-efficient communication with gRPC™ servers. It integrates gRPC services seamlessly into the Qt framework, allowing communication across different programming languages or environments regardless of whether the server is based on Qt.

Overview

gRPC is a cross-platform, high-performance Remote Procedure Call (RPC) framework. It uses the Protobuf compiler (protoc) to generate client and server interfaces from service sections in a protobuf schema for various programming languages. It is commonly used to connect services in microservices-style architectures or to link mobile applications and browsers with backend systems. For more details, see the gRPC Introduction.

Qt GRPC consists of C++ and Qt Quick APIs that handle the asynchronous nature of Remote Procedure Calls using the well-known Signals & Slots mechanism. It also provides command-line tools and a CMake API to streamline the generation of Qt-specific interfaces using protoc.

Qt GRPC currently supports client-side functionality. This means it can communicate with a gRPC-compatible server. This could be your own server with its protobuf API or a publicly available API, such as the Google APIs.

Using the Module

Module prerequisites

• protoc, the Protocol Buffers compiler, is required to run the Qt code generator plugins. See Protoc Installation.
• Optional: SSL support.
• Optional: gRPC C++ for running the examples.

C++ API

To add protobuf files to a Qt-based project and generate the required source code, use the protoc compiler along with the qtgrpcgen and qtprotobufgen Qt plugins.

• The qtprotobufgen Tool generates Qt classes from protobuf message definitions. Use the qt_add_protobuf CMake command to automate this process.
• The qtgrpcgen Tool generates interfaces from protobuf service definitions. Use the qt_add_grpc CMake command to automate this process.

A minimal example of a CMake project file that uses Qt GRPC can look like this:

cmake_minimum_required(VERSION 3.16...3.22)
project(MyProject)

find_package(Qt6 REQUIRED COMPONENTS Protobuf Grpc)
qt_standard_project_setup()

qt_add_executable(MyApp main.cpp)

qt_add_protobuf(MyApp
    PROTO_FILES
        path/to/messages.proto
)

qt_add_grpc(MyApp CLIENT
    PROTO_FILES
        path/to/service.proto
)

target_link_libraries(MyApp PRIVATE Qt6::Protobuf Qt6::Grpc)

QML API

The QML types of the module are available through the QtGrpc import. To use the types, add the following import statement to your .qml file:

import QtGrpc

Articles and Guides

• Qt GRPC Client Guide
• CMake Commands in Qt6 GRPC

References

• C++ Classes
• Qt GRPC Quick

Examples

• Qt GRPC Examples

Licenses and Attributions

The Qt GRPC module is available under commercial licenses from The Qt Company. In addition, it is available under free software licenses: The GNU General Public License, version 3. See Qt Licensing for further details.

Furthermore, Qt GRPC in Qt 6.9.0 may contain third party modules under the following permissive licenses: