POST /form-submit HTTP/1.1
Accept: */*
Authorization: Basic UG9seWNvbTo0NTY=
Content-Type: application/x-www-form-urlencoded
Referer: https://192.168.88.5/index.htm
Accept-Language: en-US,en;q=0.5
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like
Gecko
Host: 192.168.88.5
Content-Length: 32
DNT: 1
Connection: close
Cache-Control: no-cache
Cookie: Authorization=Basic UG9seWNvbTo0NTY=

15=XYZ

System.Net.ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

        ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(AcceptAllCertifications);
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;



        var requ = (HttpWebRequest)WebRequest.Create("https://192.168.88.5/form-submit");
        requ.Method = "POST";
       requ.Credentials = new NetworkCredential("Polycom", "456");

        requ.SetRawHeader("Accept", "*/*");
        requ.ServicePoint.Expect100Continue = false;
        requ.Headers.Add("Authorization", "Basic " + "UG9seWNvbTo0NTY=");
        requ.ContentType = "application/x-www-form-urlencoded";
        requ.Referer = "https://192.168.88.5/index.htm";
        requ.SetRawHeader("Accept-Language", "en-US,en;q=0.5");
        requ.UserAgent = " Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko";
        requ.SetRawHeader("Host", "192.168.88.5");
        requ.SetRawHeader("Content-Length", "6");

      //  String encoded = System.Convert.ToBase64String(System.Text.Encoding.GetEncoding("ISO-8859-1").GetBytes("Basic=" + ":" + "UG9seWNvbTo0NTY="));

        requ.SetRawHeader("DNT", "1");

        requ.Headers.Add("Cache-Control", "no - cache");

       requ.SetRawHeader("Cookie", "Authorization = Basic UG9seWNvbTo0NTY=");
        ASCIIEncoding encoding = new ASCIIEncoding();
        byte[] byte1 = encoding.GetBytes("15=ZOMBIE");

        // Set the content type of the data being posted.
        requ.ContentType = "application/x-www-form-urlencoded";

        // Set the content length of the string being posted.
       requ.ContentLength = byte1.Length;

        using (StreamWriter writer = new StreamWriter(requ.GetRequestStream()))
        {
            writer.Write("15=ZOMBIE");
        }


        var resp = (HttpWebResponse)requ.GetResponse();
        // Create a request using a URL that can receive a post.