C# HttpListener 'Bad request' problem

By : Semas
Source: Stackoverflow.com

For some reason when request is sent to HttpListener via non-standart address it returns

<h1>Bad Request (Invalid Hostname)</h1>

Example packet:

GET /index HTTP/1.1
Host: ::ffff:
Accept: */*

HTTP/1.1 400 Bad Request
Content-Type: text/html
Server: Microsoft-HTTPAPI/1.0
Date: Wed, 02 Feb 2011 19:05:18 GMT
Connection: close
Content-Length: 39

<h1>Bad Request (Invalid Hostname)</h1>

How could i solve this?

Edit: This is my code

public class Server
    private HttpListener Listener;
    private Log Log;

    public int Port = 1555;

    public Server(Log _log)
        Log = _log;

    public void Start()
        Listener = new HttpListener();
            "", Port));

            "*", Port)); //added these for testing, but still nothing

            "*", Port)); //added these for testing, but still nothing

        Listener.BeginGetContext(ProcessRequest, Listener);

        Log.Add(string.Format("HTTP Server started on port {0}",
            Port), LogType.Info, true);

    private void ProcessRequest(IAsyncResult result)
        HttpListener listener = (HttpListener)result.AsyncState;
        HttpListenerContext context = listener.EndGetContext(result);

        HttpListenerRequest request = context.Request;
        HttpListenerResponse response = context.Response;

        string[] UrlParts = request.RawUrl.Split('/');
        Response output;

        if (request.RawUrl == "/index")
            output = new Response(context.Response.OutputStream, 
                ResponseType.Stats, UrlParts, Log);

        response.ContentLength64 = output.Size;
        response.ContentType = output.Header;


        if (result.IsCompleted)
            Log.Add(String.Format("OUT > {1,15} {0,8} bytes -> {2}",
                output.Size, request.RemoteEndPoint.Address,
                request.RawUrl), LogType.Info, true);

        Listener.BeginGetContext(ProcessRequest, Listener);
By : Semas

One way this error occurs is when HTTP.SYS can not match the HTTP Host header with its list of valid UrlAcl's. This could be because of problems resolving a hostname.

  1. Related answer explaining configuration steps
  2. MSDN documentation about setting up HTTP stand-alone
  3. Fixing a “Bad Request (Invalid Hostname)” - 400 Error, on Windows IIS Server (relevant potential solutions and commentary)

You can list the mappings at the command line:

Windows XP Support Tools / 2003 Support Tools - httpcfg

httpcfg query urlacl

Included with Windows Vista / 2008 / 7+ - netsh

netsh http show urlacl

This video can help you solving your question :)
By: admin