gRPC Cronet Transport

EXPERIMENTAL: gRPC's Cronet transport is an experimental API, and is not yet integrated with our build system. Using Cronet with gRPC requires manually integrating the gRPC code in this directory into your Android application.

This code enables using the Chromium networking stack (Cronet) as the transport layer for gRPC on Android. This lets your Android app make RPCs using the same networking stack as used in the Chrome browser.

Some advantages of using Cronet with gRPC:

• Bundles an OpenSSL implementation, enabling TLS connections even on older versions of Android without additional configuration
• Robust to Android network connectivity changes
• Support for QUIC

Cronet jars are available on Google's Maven repository. See the example app at https://github.com/GoogleChrome/cronet-sample/blob/master/README.md. To use Cronet with gRPC, you will need to copy the gRPC source files contained in this directory into your application's code, as we do not currently provide a grpc-cronet dependency.

To use Cronet, you must have the ACCESS_NETWORK_STATE permission set in AndroidManifest.xml:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Once the above steps are completed, you can create a gRPC Cronet channel as follows:

import io.grpc.cronet.CronetChannelBuilder;
import org.chromium.net.ExperimentalCronetEngine;

...

ExperimentalCronetEngine engine =
    new ExperimentalCronetEngine.Builder(context /* Android Context */).build();
ManagedChannel channel = CronetChannelBuilder.forAddress("localhost", 8080, engine).build();