How to make the .net HttpClient use http 2.0?

Question

I have an asp.net web api hosted on IIS 10 (windows server 2016). When I make a GET request to this from a Microsoft Edge browser, I see that HTTP 2.0 is used in IIS logs

2015-09-20 21:57:59 100.76.48.17 GET /RestController/Native - 443 - 73.181.195.76 HTTP/2.0 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/42.0.2311.135+Safari/537.36+Edge/12.10240 - 200 0 0 7299

However, when a GET request is made through a .net 4.6 client as below,

using (var client = new HttpClient())
{
    client.BaseAddress = new Uri("https://myapp.cloudapp.net/");

    HttpResponseMessage response = await client.GetAsync("RestController/Native");
    if (response.IsSuccessStatusCode)
    {
        await response.Content.CopyToAsync(new MemoryStream(buffer));
    }
}

I see the following HTTP 1.1 log in the server logs

2015-09-20 20:57:41 100.76.48.17 GET /RestController/Native - 443 - 131.107.160.196 HTTP/1.1 - - 200 0 0 707

How can I make the .net client use HTTP/2.0 ?

score 44 · Answer 1 · answered Mar 29 '17 at 19:00

44

1.Make sure you are on the latest version of Windows 10.

2.Install WinHttpHandler:

Install-Package System.Net.Http.WinHttpHandler

3.Extend WinHttpHandler to add http2.0 support:

public class Http2CustomHandler : WinHttpHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
    {
        request.Version = new Version("2.0");
        return base.SendAsync(request, cancellationToken);
    }
}

4.Pass above handler to the HttpClient constructor

using (var httpClient = new HttpClient(new Http2CustomHandler()))
{
      // your custom code
}

answered Mar 29 '17 at 19:00

Shawinder Sekhon

1,569
12
23

Agree, this is still somehow the only way to get http2.0 support for the HttpClient in the full .net framework – Calvin Pietersen Jul 18 '18 at 23:59
Yep this works - thank you. Was scratching my head trying to understand why httpclient on 4.72 framework and win 10 did not work on http2! Seems crazy it is not in the core libraries, and btw it installs a lot of dependencies. Tested from 4.6 up. – Avner Aug 23 '18 at 04:24
1

Non-crossplatform – Kirill Belonogov Aug 18 '20 at 07:35
That works. But if you need to manage CookieContainer, you also need to set CookieUsePolicy to CookieUsePolicy.UseSpecifiedCookieContainer – gangus Jan 26 '21 at 10:14

Kevinoid · Answer 2 · 2022-05-02T21:16:58.470

In addition to WinHttpHandler (as described in Shawinder Sekhon's answer), .NET Core 3.0 includes HTTP/2 support in the default SocketsHttpHandler (#30740). Since HTTP/1.1 is still the default, either the default must be changed by setting HttpClient.DefaultRequestVersion, or Version must be changed on each request. The version can be set when the request message is created:

using (var client = new HttpClient())
{
    client.BaseAddress = new Uri("https://myapp.cloudapp.net/");

    HttpResponseMessage response = await client.SendAsync(
        new HttpRequestMessage(HttpMethod.Get, "RestController/Native")
        {
            Version = HttpVersion.Version20,
        });
    if (response.IsSuccessStatusCode)
    {
        await response.Content.CopyToAsync(new MemoryStream(buffer));
    }
}

Or by using a custom HttpMessageHandler, such as:

public class ForceHttp2Handler : DelegatingHandler
{
    public ForceHttp2Handler(HttpMessageHandler innerHandler)
        : base(innerHandler)
    {
    }

    protected override Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        request.Version = HttpVersion.Version20;
        return base.SendAsync(request, cancellationToken);
    }
}

which can delegate to SocketsHttpHandler, WinHttpHandler, or any other HttpMessageHandler which supports HTTP/2:

using (var client = new HttpClient(new ForceHttp2Handler(new SocketsHttpHandler())))
{
    client.BaseAddress = new Uri("https://myapp.cloudapp.net/");

    HttpResponseMessage response = await client.GetAsync("RestController/Native");
    if (response.IsSuccessStatusCode)
    {
        await response.Content.CopyToAsync(new MemoryStream(buffer));
    }
}

Why not change `HttpClient.DefaultRequestVersion` to `HttpVersion.Version20`? — huang, May 02 '22 at 17:43
@JoeHuang Sure, if you would like to use HTTP/2 by default for all `HttpClient`s, setting `HttpClient.DefaultRequestVersion` is a great idea. I'll add it to the answer. — Kevinoid, May 02 '22 at 21:10

score 7 · Accepted Answer · edited Sep 20 '15 at 23:41

7

HttpClient does not support HTTP/2 yet. It will be available in the next release (code name KATANA). Here is the link to their source code for the next release.

Till then, you could implement your own HttpMessageHandler object that implements HTTP/2 and pass it to the HttpClient's constructor (you probably can use their source code from KATANA).

edited Sep 20 '15 at 23:41

Mathemats

1,185
4
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answered Sep 20 '15 at 23:11

Racil Hilan

24,690
13
50
55

The repo you linked to seems to be only for the server components, not the client (there is a test client, which uses TcpClient, but not a real HttpClient) – Thomas Levesque Nov 17 '15 at 15:18
@RacilHilan Thank you for answer. "you could implement your own HttpMessageHandler object that implements HTTP/2 " regarding your this comment. could you pl elaborate more? – Rashmin Javiya Aug 24 '16 at 13:36
@RashminJaviya You can copy the code from their source code using the link in my answer and add it to your project. Remember that the code is from development, so you'll have to do all the testing and possible fixes by yourself. Obviously, that's not a simple task, but it was the only way back when this question was asked. Now, things have changed. See Oliver's answer below if it fits your needs. – Racil Hilan Aug 25 '16 at 01:57

score 5 · Answer 4 · answered Jul 19 '16 at 14:56

5

HTTP/2 looks like it will be supported in C# client calls with .NET 4.6.2

https://msdn.microsoft.com/en-us/library/ms171868(v=vs.110).aspx

HTTP/2 Support (Windows 10)

HTTP/2 is a new version of the HTTP protocol that provides much better connection utilization (fewer round-trips between client and server), resulting in lower latency web page loading for users. Web pages (as opposed to services) benefit the most from HTTP/2, since the protocol optimizes for multiple artifacts being requested as part of a single experience. HTTP/2 support has been added to ASP.NET in the .NET Framework 4.6. Because networking functionality exists at multiple layers, new features were required in Windows, in IIS, and in ASP.NET to enable HTTP/2. You must be running on Windows 10 to use HTTP/2 with ASP.NET.

HTTP/2 is also supported and on by default for Windows 10 Universal Windows Platform (UWP) apps that use the System.Net.Http.HttpClient API.

answered Jul 19 '16 at 14:56

Oliver

35,233
12
66
78

1

This is only the server-side, not the client. – csauve May 17 '18 at 22:34
1

Yeah, I am running VS2017 with .net 4.7 installed and I only see HTTP.version 1.0 and 1.1. – gwardell Dec 01 '18 at 23:43
2

Saw this comment: `To use HTTP/2 protocol support, you must use .NET Core. You must also use a supported version of Windows 10. And you need to manually specify HttpRequestMessage.Version = new Version(2,0); You can also use the separate System.Net.Http.WinHttpHandler package which provides an alternate handler for HttpClient. You need to create that WinHttpHandler and pass it into the constructor of HttpClient. This WinHttpHandler package is supported on both .NET Core .NET Framework` over here: https://github.com/dotnet/corefx/issues/4870 – Jesse Chisholm Dec 04 '18 at 19:00
Also this at same page: `you can use WinHttpHandler on .NET Framework. You must only use the SendAsync() methods from HttpClient. Those are the only ones that allow you to pass in an HttpRequestMessage. Other methods, use a default HttpRequestMessage that uses Version(1,1) only. You have to set the .Version field in HttpRequestMessage to 2.0 as indicated. You have to use a current version of Windows 10.` – Jesse Chisholm Dec 04 '18 at 19:03

How to make the .net HttpClient use http 2.0?

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