Bidirectional streaming not working when using Grpc.Net.Client.Web

[hakito]

What version of gRPC and what language are you using?

Grpc.Net.Client.Web 2.46.0
C#

What operating system (Linux, Windows,...) and version?

Windows 10 21H2

What runtime / compiler are you using (e.g. .NET Core SDK version dotnet --info)

Server: net6.0
Client: net462

What did you do?

I implemented a bidirectional streaming service using the GrpcWebHandler

service SampleService {
  rpc PingPong(stream google.protobuf.BytesValue) returns (stream google.protobuf.BytesValue) {}
}

The client sends a single request wich is handled by the server and waits for the response.

await pingPong.RequestStream.WriteAsync(new BytesValue() { Value = ByteString.CopyFromUtf8("Ping") });
await pingPong.ResponseStream.MoveNext();

The server awaits the stream from the client and returns a message

while (await requestStream.MoveNext())
{
    var buf = requestStream.Current;
    var msg = buf.Value.ToStringUtf8();
    await responseStream.WriteAsync(new BytesValue() { Value = ByteString.CopyFromUtf8($"You sent {msg} from session {session.GetString("Foo")}") });
}

What did you expect to see?

I expected a response from the server.

What did you see instead?

The client is stuck waiting endless for a response. The implementationon the server is not even called.

Anything else we should know about your project / environment?

It works properly when I either use grpc.core (wich is deprecated), or when I switch the clients target framework to net6 (without GrpcWebHandler).

[JamesNK]

That's not supported with gRPC-Web: https://docs.microsoft.com/en-us/aspnet/core/grpc/supported-platforms?view=aspnetcore-6.0#wire-formats

[hakito]

Thanks for the link. I couldn't find the info by myself. The nuget documentation is a bit misleading:

"Calling gRPC-Web with a .NET client is the same as HTTP/2 gRPC"

It should probably mention these limitations.

[JamesNK]

Ok!

#1816 and #1817