一个简单的socket的程序

      下面是MSDN中给出的一段示例程序，不过执行后总出现一个错误。
       错误：    SocketException caught!!!
                 Source : System
                 Message : 远程主机强迫关闭了一个现有的连接。
程序：server的值为 localhost  
         public static string DoSocketGet(string server)
        {
            //Set up variables and String to write to the server.
            Encoding ASCII = Encoding.ASCII;
            string Get = "GET / HTTP/1.1\r\nHost: " + server +
                         "\r\nConnection: Close\r\n\r\n";
            Byte[] ByteGet = ASCII.GetBytes(Get);
            Byte[] RecvBytes = new Byte[256];
            String strRetPage = null;
            // IPAddress and IPEndPoint represent the endpoint that will
            //   receive the request.
            // Get first IPAddress in list return by DNS.
            try
            {
                // Define those variables to be evaluated in the next for loop and 
                // then used to connect to the server. These variables are defined
                // outside the for loop to make them accessible there after.
                Socket s = null;
                IPEndPoint hostEndPoint;
                IPAddress hostAddress = null;
                int conPort = 80;                // Get DNS host information.
                IPHostEntry hostInfo = Dns.GetHostEntry(server);
                // Get the DNS IP addresses associated with the host.
                IPAddress[] IPaddresses = hostInfo.AddressList;                // Evaluate the socket and receiving host IPAddress and IPEndPoint. 
                for (int index = 0; index < IPaddresses.Length; index++)
                {
                    hostAddress = IPaddresses[index];
                    hostEndPoint = new IPEndPoint(hostAddress, conPort);
                    // Creates the Socket to send data over a TCP connection.
                    s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);                    // Connect to the host using its IPEndPoint.
                    s.Connect(hostEndPoint);                    if (!s.Connected)
                    {
                        // Connection failed, try next IPaddress.
                        strRetPage = "Unable to connect to host";
                        s = null;
                        continue;
                    }                    // Sent the GET request to the host.
                    s.Send(ByteGet, ByteGet.Length, 0);
                } // End of the for loop.                      // Receive the host home page content and loop until all the data is received.
                Int32 bytes = s.Receive(RecvBytes, RecvBytes.Length, 0);
                strRetPage = "Default HTML page on " + server + ":\r\n";
                strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0, bytes);                while (bytes > 0)
                {
                    bytes = s.Receive(RecvBytes, RecvBytes.Length, 0);
                    strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0, bytes);
                }
            } // End of the try block.            catch (SocketException e)
            {
                Console.WriteLine("SocketException caught!!!");
                Console.WriteLine("Source : " + e.Source);
                Console.WriteLine("Message : " + e.Message);
            }
            catch (ArgumentNullException e)
            {
                Console.WriteLine("ArgumentNullException caught!!!");
                Console.WriteLine("Source : " + e.Source);
                Console.WriteLine("Message : " + e.Message);
            }
            catch (NullReferenceException e)
            {
                Console.WriteLine("NullReferenceException caught!!!");
                Console.WriteLine("Source : " + e.Source);
                Console.WriteLine("Message : " + e.Message);
            }
            catch (Exception e)
            {
                Console.WriteLine("Exception caught!!!");
                Console.WriteLine("Source : " + e.Source);
                Console.WriteLine("Message : " + e.Message);
            }            return strRetPage;        }