I have a simple tcpClient and a server, both connect ok and work in unity editor but not as standalone

 using UnityEngine;
 using System.Collections;
 using System;
 using System.IO;
 using System.Net.Sockets;
 using System.Text;
 
 public class s_TCP : MonoBehaviour
 {
 
     internal Boolean socketReady = false;
     TcpClient mySocket;
     NetworkStream theStream;
     StreamWriter theWriter;
     StreamReader theReader;
     String Host = "localhost";//CLUDGE TO BE READ FROM file
     Int32 Port = 11000;
 
     public bool initialised = false;
 
     public void Initialise(string h,int p)
     {
         Host = h;
         Port = p;
         setupSocket();
         initialised = true;
         SendCommand("5");   //initialse command to server
     }
     void Update()
     {
         if (!initialised) return;
         //theStream.Flush();
         string str = readSocket();
         Debug.Log("Socket bufffer = " + str);
         if (str.Length > 0) SendMessage("DoCommand", str);
        
 
     }
 
     private void OnDestroy()
     {
         closeSocket();
     }
     // **********************************************
     void setupSocket()
     {
         try
         {
             mySocket = new TcpClient(Host, Port);
             theStream = mySocket.GetStream();
             theStream.ReadTimeout = 1;
             theWriter = new StreamWriter(theStream);
             theReader = new StreamReader(theStream);
             socketReady = true;
         }
         catch (Exception e)
         {
             Debug.LogError("Socket error: " + e);
         }
     }
     public void SendCommand(string command)
     {
         if (!socketReady)
             return;
         //String foo = theLine + "\r\n";
         theWriter.Write(command);
         theWriter.Flush();
     }
     public String readSocket()
     {
         if (!socketReady)
             return "";
         try
         {
             // Check to see if this NetworkStream is readable.
             if (theStream.CanRead)
             {
                 byte[] myReadBuffer = new byte[1024];
                 StringBuilder myCompleteMessage = new StringBuilder();
                 int numberOfBytesRead = 0;
 
                 // Incoming message may be larger than the buffer size.
                 do
                 {
                     numberOfBytesRead = theStream.Read(myReadBuffer, 0, myReadBuffer.Length);
 
                     myCompleteMessage.AppendFormat("{0}", Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead));
 
                 }
                 while (theStream.DataAvailable);
                 return myCompleteMessage.ToString();
                 
             }
             //return theReader.ReadLine();
         }
         catch (Exception e)
         {
             return "";
         }
         return "";
     }
 
     public void closeSocket()
     {
         if (!socketReady)
             return;
         theWriter.Close();
         theReader.Close();
         mySocket.Close();
         socketReady = false;
     }
 } // end class s_TCP