diff --git a/MtClient/MtMessage.cs b/MtClient/MtMessage.cs
index 77b09b9a..310bba7b 100755
--- a/MtClient/MtMessage.cs
+++ b/MtClient/MtMessage.cs
@@ -1,4 +1,7 @@
-namespace MtClient
+using System.ComponentModel.Design;
+using System.Data;
+
+namespace MtClient
 {
     public enum MessageType
     {
@@ -8,6 +11,7 @@
         ExpertList = 3,
         ExpertAdded = 4,
         ExpertRemoved = 5,
+        ClientReady = 6
     }
 
     public abstract class MtMessage
@@ -37,6 +41,16 @@
         }
     }
 
+    public class MtClientReady : MtMessage
+    {
+        public override MessageType MsgType => MessageType.ClientReady;
+
+        protected override string GetMessageBody()
+        {
+            return string.Empty;
+        }
+    }
+
     public class MtEvent(int expertHandle, int eventType, string payload) : MtMessage
     {
         public override MessageType MsgType => MessageType.Event;
@@ -101,11 +115,11 @@
         }
     }
 
-    public class MtExpertListMsg(List<int> experts) : MtMessage
+    public class MtExpertListMsg(HashSet<int> experts) : MtMessage
     {
         public override MessageType MsgType => MessageType.ExpertList;
 
-        public List<int> Experts { private set; get; } = experts;
+        public HashSet<int> Experts { private set; get; } = experts;
 
         protected override string GetMessageBody()
         {
@@ -115,7 +129,7 @@
         public static MtMessage? Parse(string payload)
         {
             var pieces = payload.Split(",");
-            List<int> handles = [];
+            HashSet<int> handles = [];
             foreach (var p in pieces)
             {
                 if (int.TryParse(p, out int expertHandle) == false)
diff --git a/MtClient/MtRpcClient.cs b/MtClient/MtRpcClient.cs
index a2bbac7e..b618b8e6 100755
--- a/MtClient/MtRpcClient.cs
+++ b/MtClient/MtRpcClient.cs
@@ -40,7 +40,8 @@ namespace MtClient
 
             try
             {
-                await ws_.CloseAsync(WebSocketCloseStatus.NormalClosure, null, CancellationToken.None);
+                if (ws_.State == WebSocketState.Open)
+                    await ws_.CloseAsync(WebSocketCloseStatus.NormalClosure, null, CancellationToken.None);
                 ws_.Dispose();
             }
             catch (Exception ex)
@@ -103,6 +104,7 @@ namespace MtClient
                     {
                         Log($"DoReceive: close signal {result.CloseStatusDescription}");
                         await ws_.CloseAsync(WebSocketCloseStatus.NormalClosure, null, CancellationToken.None);
+                        Disconnected?.Invoke(this, EventArgs.Empty);
                         break;
                     }
                     else
@@ -169,6 +171,7 @@ namespace MtClient
 
         public event EventHandler<MtMessage>? MessageReceived;
         public event EventHandler<EventArgs>? ConnectionFailed;
+        public event EventHandler<EventArgs>? Disconnected;
 
         private readonly ClientWebSocket ws_ = new();
         private readonly string host_;