Get Domain Name using asp.net in Generic handler page - asp.net

Question

I want to get domain name not for remote ip. i have two domain(website). example www.a1.com and www.a2.com. in a2 domain send a request to a1 domain's page like GetRequest.ashx
the example of http request is
http://www.a1.com/GetRequest.ashx?username=bala&password=123456
in my GetRequest.ashx page example coding
<%# WebHandler Language="VB" Class="Handler" %>
Imports System
Imports System.Web
Public Class GetRequest : Implements IHttpHandler
Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
context.Response.ContentType = "text/plain"
Dim username As String = context.Request.QueryString("username")
Dim password As String = context.Request.QueryString("password")
**'//Here i need a coding to get requested domain name that is who send the request to my page**
End Sub
Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
Get
Return False
End Get
End Property
End Class
i already use the following coding but not solve my problem. because it return ip address. i need domain only not for ip.
context.Request.ServerVariables("REMOTE_ADDR")
context.Request.ServerVariables("REMOTE_HOST")
Dim domain As String
Dim url As Uri = HttpContext.Current.Request.Url
domain = url.AbsoluteUri.Replace(url.PathAndQuery, String.Empty)
the variable domain contain www.a1.com but i need www.a2.com
use google analytics api to solve my problem? then how to use this api can any one explain

Answer 1

Page.Request.Url.Host contains the host name of the url (www.a1.com in your example)
If a request on the www.a2.com site calls a page on the www.a1.com site, the hostname will always be www.a1.com since that is the host that was used to call the page. I recommend passing a query string variable if you need to know that the request originated from www.a2.com.

Answer 2

You can access the request object through HttpContext, like so:
EDIT: Changed to get host name of referring URL
string host = HttpContext.Current.Request.UrlReferrer.Host;
EDIT: UrlReferrer is returning null. Alternative using HTTP_REFERER:
if (!String.IsNullOrEmpty(Request.ServerVariables["HTTP_REFERER"]))
{
Uri referringUrl = new Uri(Request.ServerVariables["HTTP_REFERER"]);
string referringHostName = referringUrl .Host;
}

Answer 3

Check the Referrer:
HttpContext.Current.Request.UrlReferrer.Host
Inside your code:
Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
context.Response.ContentType = "text/plain"
Dim username As String = context.Request.QueryString("username")
Dim password As String = context.Request.QueryString("password")
**'//Here i need a coding to get requested domain name that is who send the request to my page**
Dim domain as string = context.Request.UrlReferrer.Host
End Sub