title: The connection to the OPC server drops after first connection throurg the WCF service
body: <p>I have a WCF service as an OPC client that interfaces with an OPC DA server, also I have a WCF client that interacts with WCF and launches it (uses its methods)
  The problem is that:
  When I use WCF method <code>connectToOPC()</code> at first time, the connection can be break after few seconds, or not. <code>DataChange</code> stops coming. 
  But when I restart <code>connectToOPC</code>, the connection remains active and does not fall. What happens and why?</p>
  
  <p>WCF Service:</p>
  
  <pre><code>public void connectToOPC(string OPCUrl, int GroupUpdateTime)
  {
      try
      {
          Main(OPCUrl, GroupUpdateTime);
      }
      catch (Exception ex) { Log(ex.Message, ""); }
  }
  
  public bool Run(string OPCUrl, int GroupUpdateTime)
      {
          try
          {
              url = new Opc.URL(OPCUrl);
              server.Connect(url, new Opc.ConnectData(new System.Net.NetworkCredential()));
  
              groupState = new Opc.Da.SubscriptionState();
              groupState.Name = "MyGroup";
              groupState.UpdateRate = GroupUpdateTime;
              groupState.Active = true;
  
              groupRead = (Opc.Da.Subscription)server.CreateSubscription(groupState);
              groupRead.DataChanged += new Opc.Da.DataChangedEventHandler(group_DataChanged);
  
              items = new Opc.Da.Item[ListOfTags.Count];
  
              for (int i = 0; i &lt; ListOfTags.Count; i++)
              {
                  items[i] = new Opc.Da.Item();
                  items[i].ItemName = ListOfTags[i];
              }
              items = groupRead.AddItems(items);
          }
          catch (Exception ex)
          {
              Log(ex.Message, "");
              return false;
          }
          return true;
      }
          void group_DataChanged(object subscriptionHandle, object requestHandle,Opc.Da.ItemValueResult[] values)
      {
          //its stops here at first time  
      }
  </code></pre>
  
  <p>And code of WCF client(WPF):</p>
  
  <pre><code>public partial class MainWindow : Window
  {
      OPCClient client;
  
      public MainWindow()
      {
          InitializeComponent();
  
          client = new OPCClient("BasicHttpBinding_IOPC");
      }
  
      private void buttonOpcRun_Click(object sender, RoutedEventArgs e)
      {
          try
          {
              GroupUpdateTime = Convert.ToInt32(textBoxUpdateGroupTime.Text);
              client.connectToOPC(OPCUrl, GroupUpdateTime);
          }
          catch (Exception ex)
          {
              System.Windows.MessageBox.Show(ex + "");
          }
      }
  }
  </code></pre>