C# How to spoof IP address for WebRequest

Question

I have asp.net website hosted and I am making WebRequest to post data and get response. The website is having IP filtering. I want to spoof sender IP address for testing purpose. Is it possible to do it programmatically or I have to use any tool.

public string GetResponse(string request)
{  
    lock (Obj)  
    {  
        request = request + _dataControlInfo.SendEndingWith;  
        Logger.Info(request);  
        var req = (HttpWebRequest)WebRequest.Create(_serviceUrl);  
        req.Headers.Add("SOAPAction", "\"\"");  
        req.ContentType = "text/xml;charset=\"utf-8\"";  
        req.Accept = "text/xml";  
        req.Method = "POST";  
        var stm = req.GetRequestStream();  
        var bytes = UtfEncoding.StringToUtf8ByteArray(request);  
        stm.Write(bytes, 0, bytes.Length);  
        stm.Close();  
        var resp = req.GetResponse();  
        var stmr = new StreamReader(resp.GetResponseStream());  
        var strResponseXml = stmr.ReadToEnd();  
        Logger.Info(strResponseXml);  
        return strResponseXml;  
    }  
}  

Please specify any possibilities.

Answer 1

What your looking for is SharpPCap which is a .NET port of WinPCap.. it allows you to do IP Spoofing, which is what your talking about. The only problem with your idea is that you wont be able to get a response back. You can send requests out, but if you dont have a proper return address then the request will be lost in the interwebs.

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Edit

To do this yoruself w/out the help of a library you will need to construct the raw packets yourself. This has been answered here.

Answer 2

If you're expecting to get a response, then no. Without the correct IP address, the server won't send the response to the correct destination.

If you insist on trying anyway, see this article for programmatically setting the client's IP address.