HTTP/2 over TLS was not negotiated on an HTTP/2-only endpoint.

Problem: On the server side

Microsoft.AspNetCore.Server.Kestrel[0]
      HTTP/2 over TLS was not negotiated on an HTTP/2-only endpoint.

Attempts to solve:

1. With .cshtml

@page
@model IndexModel
@{
    ViewData["Title"] = "Home page";
}
<h1>Hello, gRPC!</h1>
@using Tasly.Service
@using Grpc.Core

<button class="btn btn-primary" onclick="@SayHello()">RUN</button>

<hr />

<p>@Greeting</p>

@functions {

    private string Greeting;

    async Task SayHello()
    {
        var channel = new Channel("localhost:5001", ChannelCredentials.Insecure);
        var client = new Greeter.GreeterClient(channel);

        var reply = await client.SayHelloAsync(new HelloRequest { Name = "Blazor gRPC Client" });
        Greeting = reply.Message;

        await channel.ShutdownAsync();
    }

}

1. The same with .razor (but it doesn’t work) or I used it incorrectly.

---

If you have any suggestions about how to fix, or if you need more information, please let me know.

[kmudayakumar]

This issue occurred for me even though I have used Grpc.Net.Client package. In fact the sample downloaded from https://github.com/aspnet/AspNetCore.Docs also have the same problem.

[StingyJack]

@AbdoDabbas On the service I had this in the appSettings.json

{ ...
  "Kestrel": {
    "EndpointDefaults": {
      "Protocols": "Http2"
    }
  }

The c# client had to be changed to use http2 messages like this…

var req = new HttpRequestMessage(HttpMethod.Get, _myEndpoint) { Version = new Version(2, 0) };
var response = await _httpClient.SendAsync(req).ConfigureAwait(false);