ASP.NET Core WebSockets on IIS 7.5

Question

I know the WebSockets are supported only on Windows 8 and higher. But sometimes you just can't upgrade the system in large organization. So I tried implement WebSockets on ASP.NET Core app. I take NuGet package "AspNetCore.WebSockets.Server" and run as a self-hosted app on Windows 7 and everything works well. But hosting on IIS7.5 on the same machine wont allow me to upgrade HTTP connection to WebSocket. Even if I try to simulate the handshake the IIS simple removes my "Sec-WebSocket-Accept" header.

static async Task Acceptor(HttpContext hc, Func<Task> next)
{
    StringValues secWebSocketKey;
    if(hc.Request.Headers.TryGetValue("Sec-WebSocket-Key", out secWebSocketKey))
    {
        hc.Response.StatusCode = 101;
        hc.Response.Headers.Clear();
        hc.Response.Headers.Add("Upgrade", new StringValues("websocket"));
        hc.Response.Headers.Add("Connection", new StringValues("Upgrade"));

        // Disappears on client
        hc.Response.Headers.Add("Sec-WebSocket-Accept", new StringValues(GetSecWebSocketAccept(secWebSocketKey[0])));
    }

    await next();
}

I definitely sure IIS7.5 physically can manage WebSockets if they was implemented by developer and that behavior (header removal) looks like a dirty trick from Microsoft

Answer 1

I am afraid you need IIS 8

With the release of Windows Server 2012 and Windows 8, Internet Information Services (IIS) 8.0 has added support for the WebSocket Protocol.

https://www.iis.net/learn/get-started/whats-new-in-iis-8/iis-80-websocket-protocol-support

The new http.sys is the one that can turn a regular HTTP connection into a binary communication for websockets. Although you can implement your own thing, you cannot hook it into http.sys.