How to set custom "Host" header in HttpWebRequest?
Solution 1
There is a roundabout way to do this, as described here:
http://blogs.msdn.com/feroze_daud/archive/2005/03/31/404328.aspx
However, the next version of the framework (.NET Framework 4.0) will make it easier.
http://blogs.msdn.com/ncl/archive/2009/07/20/new-ncl-features-in-net-4-0-beta-2.aspx
Hope this helps.
Solution 2
Necromancing.
For those still on .NET 2.0
It is in fact quite easy, if you know how.
Problem is, you can't set the host header, because the framework won't let you change the value at runtime. (.net framework 4.0+ will let you override host in a httpwebrequest).
Next attempt will be setting the header with reflection, to get around it, which will let you change the header value. But at runtime, it will overwrite this value with the host part of the url, which means reflection will bring you nothing.
If the dns-name doesn't exist, which is quite frankly the only case in which you want to do this in the first place, you can't set it, because .NET can't resolve it, and you can't override the .NET DNS resolver.
But what you can do, is setting a webproxy with the exact same IP as the destination server.
So, if your server IP is 28.14.88.71:
public class myweb : System.Net.WebClient
{
protected override System.Net.WebRequest GetWebRequest(System.Uri address)
{
System.Net.WebRequest request = (System.Net.WebRequest)base.GetWebRequest(address);
//string host = "redmine.nonexistantdomain.com";
//request.Headers.GetType().InvokeMember("ChangeInternal",
// System.Reflection.BindingFlags.NonPublic |
// System.Reflection.BindingFlags.Instance |
// System.Reflection.BindingFlags.InvokeMethod, null,
// request.Headers, new object[] { "Host", host }
//);
//server IP and port
request.Proxy = new System.Net.WebProxy("http://28.14.88.71:80");
// .NET 4.0 only
System.Net.HttpWebRequest foo = (System.Net.HttpWebRequest)request;
//foo.Host = host;
// The below reflection-based operation is not necessary,
// if the server speaks HTTP 1.1 correctly
// and the firewall doesn't interfere
// https://yoursunny.com/t/2009/HttpWebRequest-IP/
System.Reflection.FieldInfo horribleProxyServicePoint = (typeof(System.Net.ServicePoint))
.GetField("m_ProxyServicePoint", System.Reflection.BindingFlags.NonPublic |
System.Reflection.BindingFlags.Instance);
horribleProxyServicePoint.SetValue(foo.ServicePoint, false);
return foo;
return request;
}
}
and voila, now
myweb wc = new myweb();
string str = wc.DownloadString("http://redmine.non-existant-domain.com");
and you get the correct page back, if 28.14.88.71 is a webserver with virtual name-based hosting (based on http-host-header).
Solution 3
You can use this hack, designed for solve this problem in .Net 3.5 .
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Reflection;
namespace ConsoleApplication6
{
class Program
{
static void Main(string[] args)
{
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://198.252.206.16");
FieldInfo headersFieldInfo = request.GetType().GetField("_HttpRequestHeaders", System.Reflection.BindingFlags.NonPublic
| System.Reflection.BindingFlags.Instance
| System.Reflection.BindingFlags.GetField);
CusteredHeaderCollection WssHeaders = new CusteredHeaderCollection("stackoverflow.com");
headersFieldInfo.SetValue(request, WssHeaders);
request.Proxy = null;
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader sr = new StreamReader(response.GetResponseStream());
string result = sr.ReadToEnd();
Console.WriteLine(result);
Console.ReadLine();
}
public class CusteredHeaderCollection : WebHeaderCollection
{
public bool HostHeaderValueReplaced { get;private set; }
public string ClusterUrl { get; private set; }
public CusteredHeaderCollection(string commonClusterUrl) : base()
{
if (string.IsNullOrEmpty("commonClusterUrl"))
throw new ArgumentNullException("commonClusterUrl");
this.ClusterUrl = commonClusterUrl;
}
public override string ToString()
{
this["Host"] = this.ClusterUrl;
string tmp = base.ToString();
this.HostHeaderValueReplaced = true;
return tmp;
}
}
}
}
Solution 4
WebClient allows it.
var client = new WebClient();
client.Headers.Add( "Host", WebHeader );
I couldn't tell you why. The documentation clearly states that Host is a system header.
Comments
-
Djonatas Tenfen about 4 years
How can I set a custom Host header in HttpWebRequest? I know that normally this class doesn't allow you to do so but is there anyway to use reflection or something like that without actually need me to send the whole packet with TCPClient?
-
Djonatas Tenfen over 14 yearsI've seen that page although there are lots of problems in that workaround beside of that it's a really dirty workaround :)
-
Stefan Steiger over 7 yearsThat's because it doesn't work - exception host header cannot be directly changed.
-
Admin over 7 yearsNice, for .NET 2.0. Obviously, this won't work if you actually need to use a proxy-server ;) Just upgrade to .NET 4.5 already - WebRequest and WebClient are both deprecated anyway.
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Mikhail almost 7 yearsNot works. ArgumentException: This header must be modified with the appropiate property.
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Patrick almost 7 yearsIt literally works. As I said, running in production. System.Net.WebClient. Target 3.5