can anyone see why this code is not working?

it fails around line 13 - Exception: Unable to connect to the remote host

looked online but nothing specific as to what causes this error.

im trying to post this xml data to a another site via a web service.

Code Csharp:
 
 
1    protected void HttpRequest(String XMLFile)
2        {
3            try
4            {
5                HttpWebRequest Request1 = (HttpWebRequest)WebRequest.Create("http://www.txttools.co.uk/connectors/soap/addressbook");           
6                byte[] Data = System.Text.Encoding.ASCII.GetBytes(GetData(XMLFile));
7                Request1.Method = "POST";
8                Request1.ContentType = "text/xml";   // application/x-www-form-urlencoded
9                Request1.ContentLength = Data.Length;
10               Request1.KeepAlive = true;
11               Request1.SendChunked = true;
12              
13               Stream StreamWriter1 = Request1.GetRequestStream();
14               StreamWriter1.Write(Data, 0, Data.Length);
15               StreamWriter1.Close();
16              
17               HttpWebResponse Response1 =(HttpWebResponse) Request1.GetResponse();
18               Stream responseStream = Response1.GetResponseStream();
19               StreamReader reader = new StreamReader(responseStream);
20               string hello = reader.ReadToEnd();
21               Response.Write(hello);
22           }
23           catch (Exception ex)
24           {
25               Response.Write("Exception: " + ex.Message);
26           }
27           finally
28           {
29              
30           }
31       }