help me to debug this...,A first chance exception of type 'System.Net.WebException' occurred in System.dll.

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C#3.5

aim of my project is send an SMS to mobile phone, when traffic occurs in network. it includes network analyzer. All are perfectly working but SMS will not be sent. It shows A first chance exception of type 'System.Net.WebException' occurred in System.dll error message. how to fix it.?
my coding:

bool verifySettings(RawSocket.PacketArrivedEventArgs packet)
{
   bool verified = false;
   if (Properties.Settings.Default.Protocol.Equals("all"))
      verified = true;
   else
      foreach (String s in Properties.Settings.Default.Protocol.Split(';'))
         if (s.Equals(packet.Protocol))
            verified = true;

   if (!Properties.Settings.Default.MobileNo.Equals("none"))
   {
      if (!(Properties.Settings.Default.DenyFromData.Equals("none") || Properties.Settings.Default.DenyToData.Equals("none")))
      {
         String data = Encoding.ASCII.GetString(packet.ReceiveBuffer);
         if (data.IndexOf(Properties.Settings.Default.DenyFromData) >= -1 || data.IndexOf(Properties.Settings.Default.DenyToData) >= -1)
         {
            sendSMS(Properties.Settings.Default.MobileNo, "Denied Data is travelling from " + packet.DestinationAddress + " to " + packet.OriginationAddress);
         }
      }

      if (!Properties.Settings.Default.DenyFromIP.Equals("none"))
      {
         if (Properties.Settings.Default.DenyFromIP.IndexOf(packet.OriginationAddress) > -1)
            sendSMS(Properties.Settings.Default.MobileNo, "Data from a Denied IP address : " + packet.DestinationAddress);
      }

      if (!Properties.Settings.Default.DenyToIP.Equals("none"))
      {
         if (Properties.Settings.Default.DenyToIP.IndexOf(packet.OriginationAddress) > -1)
            sendSMS(Properties.Settings.Default.MobileNo, "Data to a Denied IP address : "+packet.OriginationAddress);
      }

   }

   return verified;
}
        
bool sendSMS(String MobileNo, String Message)
{
   bool sent = false;
   HttpWebRequest request = default(HttpWebRequest);
   HttpWebResponse response = null;
   string url = null;
   string username = null;
   string password = null;
   string host = null;
   string originator = null;            
            
   try
   {
      host = "http://127.0.0.1:9501";
      originator = "99994905708";    //Sender Mobile Number
      username = "admin";
      password = "abc123";

      url = host + "/api?action=sendmessage&" + "username=" + HttpUtility.UrlEncode(username) + "&password=" + HttpUtility.UrlEncode(password) + "&recipient=" + HttpUtility.UrlEncode(MobileNo) + "&messagetype=SMS:TEXT" + "&messagedata=" + HttpUtility.UrlEncode(Message) + "&originator=" + HttpUtility.UrlEncode(originator) + "&serviceprovider=GSMModem1" + "&responseformat=html";
      request = (HttpWebRequest)WebRequest.Create(url);
      response = (HttpWebResponse)request.GetResponse();
      sent = true;
   }
   catch (Exception)
   {
      sent = false;
   }
   
   return sent;
}