.NET Core 3 fails accepting Java client calls

Issue description

We are transitioning our micro-services from .NET Core 2.1 with the old gRPC dotnet nuget, to .NET Core 3.0 with the inbuilt support for gRPC in Kestrel.

One of our clients is Android app. When tried to connect from the Android client:

Failed... : 
io.grpc.StatusRuntimeException: INTERNAL: Protocol error
Rst Stream
	at io.grpc.stub.ClientCalls.toStatusRuntimeException(ClientCalls.java:235)
	at io.grpc.stub.ClientCalls.getUnchecked(ClientCalls.java:216)
	at io.grpc.stub.ClientCalls.blockingUnaryCall(ClientCalls.java:141)
	at io.grpc.examples.helloworld.GreeterGrpc$GreeterBlockingStub.sayHello(GreeterGrpc.java:228)
	at io.grpc.helloworldexample.HelloworldActivity$GrpcTask.doInBackground(HelloworldActivity.java:90)
	at io.grpc.helloworldexample.HelloworldActivity$GrpcTask.doInBackground(HelloworldActivity.java:72)
	at android.os.AsyncTask$2.call(AsyncTask.java:333)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
	at java.lang.Thread.run(Thread.java:764)

Set up is Development, it’s over HTTP, no TLS has been enabled.

Someone reported the same issue on stackoverflow for Kotlin

I want to point out that we tried the same Stubs with different clients like .NET Core 3.0/ Swift and even BlazorRPC and they worked without an issue.

General version information

gRPC: Java uses : 1.23.0 .NET uses: 2.23.2 Windows 10 Docker for Win 19.03.2

Images used for building the docker final image: mcr.microsoft.com/dotnet/core/aspnet:3.0-buster-slim AS base mcr.microsoft.com/dotnet/core/sdk:3.0-buster AS build

How to reproduce:

1. Download .NET Greeter example: https://github.com/grpc/grpc-dotnet/tree/master/examples/Greeter
2. Download Java Greeter for Android: https://github.com/grpc/grpc-java/tree/master/examples/android/helloworld
3. Modify proto Greeter file in .NET example by adding these extra options before the package Name:

syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package Greet;

1. Make sure Java client Uses the modified proto to generate Stubs.
2. Run server in Docker
3. Get port of container and connect via Local network using IPv4 Address
4. Call server from Client

[ivan-penchev]

Interesting suggestion for a solution? Because I could swear I have done it. Maybe I have missed something ? How do you disable TLS on the server explicitly? Currently Java builds the channel like this:

  ManagedChannelBuilder managedChannelBuilder = ManagedChannelBuilder
                    .forAddress(mUrl, mPort)
                    .keepAliveTime(3, TimeUnit.MINUTES)
                    .keepAliveTimeout(30, TimeUnit.SECONDS).
                    .usePlaintext()
                    .build();

On the server side I use the appsettings.json

{
  "Kestrel": {
    "Endpoints": {
      "Grpc": {
        "Url": "http://*:13377",
        "Protocols": "Http2"
      }
    }
  }
}

As you can notice there is no “Certificate” path provided. @JamesNK thank you for the assistance.

[JamesNK]

I’ve managed to recreate this. I suspect the issue is in Kestrel’s implementation of HTTP/2. Something about the HTTP/2 request from the Android client is causing Kestrel to reject it.

Kestrel issue: https://github.com/aspnet/AspNetCore/issues/14745