I am reposting my previous post with some correction:

I've to programmatically login to a third party web app (Tomcat/apache) and
take the user to a landing page. I am able to programatically login
succesfullly but it takes me to the landing page but the third part app says
my request is not authenticated. If I look at the logs on Tomcat side, I see
the cookies are getting lost  somewhere even though I pass the cookies
between successive requests. I would  appreciate any comments or suggestion
regarading how to take the user successfully to the landing page.
       
       string url = "http://10.112.60.86:8080/PCC/servlet/tpservlet";
       HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);

     
       CookieContainer CookieC = new CookieContainer();


       string data =
String.Format("USERID={0}&transactiontype={2}&FIID={3}&AUTHENTICATIONURL={4}&TARGET={5}",
"DDBDB3099C5C04D36B91C0EA786C0996", "729E13B7AFB57796A30",
"UserInqAuthActionBean", "1111",
"http://atl50test2/CLKPCB/111111118/Site/TransfersPayments/opserror.asp",
"BillPay.viewPayees");
       byte[] buffer = Encoding.UTF8.GetBytes(data);
       req.AllowAutoRedirect = false;
       req.KeepAlive = true;
       req.Method = "POST";
       req.ContentType = "application/x-www-form-urlencoded";
       req.ContentLength = buffer.Length;
       req.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1;
.NET CLR 1.1.4322; .NET CLR 2.0.50727)";

       req.CookieContainer = CookieC;

       Stream reqst = req.GetRequestStream(); // add form data to request
stream
       reqst.Write(buffer, 0, buffer.Length);
       reqst.Flush();
       reqst.Close();

       HttpWebResponse res = (HttpWebResponse)req.GetResponse();

       
        string landingpage= res.Headers["Location"];
       CookieC.Add(res.Cookies);

       
       foreach (Cookie cook in CookieC.GetCookies(req.RequestUri))
       {
           HttpCookie cookie = new HttpCookie(cook.Name);
           cookie.Name = cook.Name;
           cookie.Value = cook.Value;
           cookie.Domain = cook.Domain;
           cookie.Expires = cook.Expires;
           cookie.Path = cook.Path;
           cookie.Secure = cook.Secure;

           String str = String.Format("Name {0}: Value {1}: Domain
{2}<BR>", cookie.Name, cookie.Value, cookie.Domain);

           HttpContext.Current.Response.AppendCookie(cookie);

       }
//This statement redirects to third party web server but it thinks that user
is not authenticate
       Response.Redirect(landingpage);