c# - .NET 5 GRPC client call throws exception: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled

Question

This is my first gRPC application. I'm attempting to invoke a server-streaming RPC call from a .NET 5 gRPC client (Grpc.Net.Client 2.35.0) which results in the following exception in my local development environment:

Grpc.Core.RpcException: Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled."

This occurs whether or not the server application is running. Here is the code I'm using to make the call:

using var channel = GrpcChannel.ForAddress(@"http://localhost:5000");
var client = new AlgorithmRunner.AlgorithmRunnerClient(channel);
using var call = client.RunAlgorithm(new RunAlgorithmRequest());

while (await call.ResponseStream.MoveNext())
{

}

My understanding is that .NET 5 gRPC is supposed to have HTTP/2 enabled by default: why does the exception indicate that HTTP/2 is not enabled and how do I resolve it?

Answer 1

After further investigation, this appears related to proxy settings on my machine related to my company's network setup. Specifically, I have the following environment variables defined:

http_proxy https_proxy

.NET populates the HttpClient DefaultProxy from these environment variables. My company proxy appears to be interfering with HTTP/2 (unsupported?), preventing gRPC from working correctly. The workaround for local development is to manually set the default proxy for the HttpClient before making the gRPC call:

HttpClient.DefaultProxy = new WebProxy();
                
using var channel = GrpcChannel.ForAddress(@"http://localhost:5000");
var client = new AlgorithmRunner.AlgorithmRunnerClient(channel);
using var call = client.RunAlgorithm(new RunAlgorithmRequest());

This may represent a general problem with using gRPC through certain types of proxies.