update

MySolution/ConsoleApp/TelnetSamples/AsyncSocketTelnetClient.cs

@@ -12,9 +12,10 @@ namespace ConsoleApp.TelnetSamples
 {
 	internal class AsyncSocketTelnetClient : IAsyncTelnetClient
 	{
-		private readonly CancellationTokenSource CTS = new CancellationTokenSource();
+		private CancellationTokenSource _cts;
 
 		public event EventHandler<string> MessageCallback;
+		public event EventHandler<Exception> ErrorCallback;
 
         private Socket _socket;
 
@@ -22,7 +23,7 @@ namespace ConsoleApp.TelnetSamples
 		{
 			try
 			{
-				Close();
+				//Close();
 
 				_socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
 				_socket.ReceiveTimeout = 1000;
@@ -31,11 +32,13 @@ namespace ConsoleApp.TelnetSamples
 				IPEndPoint iPEndPoint = new IPEndPoint(ipAddress, port);
 				await _socket.ConnectAsync(iPEndPoint);
 
-				Task.Run(ReadAsync);
+				_cts = new CancellationTokenSource();
+				Task.Run(ReadAsync, _cts.Token);
 			}
-			catch (Exception)
+			catch (Exception ex)
 			{
-				throw;
+                if (this.ErrorCallback != null)
+                    this.ErrorCallback(this, ex);
             }
 		}
 
@@ -43,14 +46,21 @@ namespace ConsoleApp.TelnetSamples
 		{
 			try
 			{
-
 				StringBuilder sb = new StringBuilder();
 				byte[] readBuffer = new byte[1024];
 				while (true)
 				{
-					int bytesRead = await _socket.ReceiveAsync(readBuffer);
+					if (_cts != null && _cts.IsCancellationRequested)
+						break;
+
+					int bytesRead = _cts != null && _cts.IsCancellationRequested ? 0 : await _socket.ReceiveAsync(readBuffer);
 					if (bytesRead < 1)
+					{
+						if (sb.Length > 0 && this.MessageCallback != null)
+							this.MessageCallback(this, sb.ToString());
+
                         break;
+                    }
 
                     string data = Encoding.ASCII.GetString(readBuffer, 0, bytesRead);
 					sb.Append(data);
@@ -69,9 +79,10 @@ namespace ConsoleApp.TelnetSamples
 					sb.Clear();
 				}
 			}
-			catch (Exception)
+            catch (Exception ex)
             {
-				throw;
+                if (this.ErrorCallback != null)
+                    this.ErrorCallback(this, ex);
             }
         }
 
@@ -79,13 +90,18 @@ namespace ConsoleApp.TelnetSamples
 		{
 			try
 			{
+				command = command.Replace(" ", "");
+				if (string.IsNullOrEmpty(command))
+					return;
+
 				command += "\r\n";
 				byte[] sendBytes = Encoding.ASCII.GetBytes(command);
 				await _socket.SendAsync(sendBytes);
 			}
-			catch (Exception)
+            catch (Exception ex)
             {
-				throw;
+                if (this.ErrorCallback != null)
+                    this.ErrorCallback(this, ex);
             }
         }
 
@@ -96,13 +112,16 @@ namespace ConsoleApp.TelnetSamples
 				if (_socket == null)
 					return;
 
+				_cts.Cancel();
+
 				_socket.Shutdown(SocketShutdown.Both);
 				_socket.Close();
 				_socket.Dispose();
 			}
-			catch (Exception)
+            catch (Exception ex)
             {
-				throw;
+                if (this.ErrorCallback != null)
+                    this.ErrorCallback(this, ex);
             }
         }
 	}

MySolution/ConsoleApp/TelnetSamples/AsyncStreamTelnetClient.cs

@@ -10,6 +10,7 @@ namespace ConsoleApp.TelnetSamples
     internal class AsyncStreamTelnetClient : IAsyncTelnetClient
 	{
 		public event EventHandler<string> MessageCallback;
+        public event EventHandler<Exception> ErrorCallback;
 
         private TcpClient _client;
 		private NetworkStream _stream; 

MySolution/ConsoleApp/TelnetSamples/AsyncTelnetConsole.cs

@@ -20,21 +20,31 @@ namespace ConsoleApp.TelnetSamples
             try
             {
                 _client.MessageCallback += On_Receive;
+                _client.ErrorCallback += On_ErrorCallback;
                 _client.Connect(ip, port);
 
                 while (true)
                 {
-                    string command = Console.ReadLine();
+                    string command = Console.ReadLine().ToLower();
                     if (command == "quit" || command == "exit")
                         break;
-
+                    else if (command == "disconnect" || command == "disconn")
+                        _client.Close();
+                    else if (command == "connect" || command == "conn")
+                        _client.Connect(ip, port);
+                    else
                         _client.SendCommand(command);
                 }
             }
-            catch (Exception)
+            catch (Exception ex)
             {
-                throw;
+                Console.WriteLine($"[ERR] {ex.Message}");
+            }
         }
+
+        private void On_ErrorCallback(object? sender, Exception e)
+        {
+            Console.WriteLine(e.Message);
         }
 
         private void On_Receive(object? sender, string e)

MySolution/ConsoleApp/TelnetSamples/IAsyncTelnetClient.cs

@@ -9,6 +9,7 @@ namespace ConsoleApp.TelnetSamples
 	public interface IAsyncTelnetClient
 	{
 		public event EventHandler<string> MessageCallback;
+		public event EventHandler<Exception> ErrorCallback;
 
 		void Connect(string ip, int port = 23);
 		void SendCommand(string command);

MySolution/ConsoleApp/TelnetSamples/TelnetConsole.cs

@@ -24,10 +24,14 @@ namespace ConsoleApp.TelnetSamples
 
 				while (true)
 				{
-					string command = Console.ReadLine();
+					string command = Console.ReadLine().ToLower();
 					if (command == "quit" || command == "exit")
 						break;
-
+					else if (command == "disconnect" || command == "disconn")
+						_client.Close();
+					else if (command == "connect" || command == "conn")
+						_client.Connect(ip, port);
+					else
 						Console.Write(_client.SendCommand(command));
 				}
 			}

MySolution/SerialComApp/SerialCommApp.Designer.cs

@@ -33,6 +33,7 @@
             this.tableLayoutPanel2 = new System.Windows.Forms.TableLayoutPanel();
             this.connectButton = new System.Windows.Forms.Button();
             this.panel1 = new System.Windows.Forms.Panel();
+            this.portRefreshButton = new System.Windows.Forms.Button();
             this.settingButton = new System.Windows.Forms.Button();
             this.label1 = new System.Windows.Forms.Label();
             this.portComboBox = new System.Windows.Forms.ComboBox();
@@ -40,7 +41,6 @@
             this.sendButton = new System.Windows.Forms.Button();
             this.commandText = new System.Windows.Forms.TextBox();
             this.printText = new System.Windows.Forms.TextBox();
-			this.portRefreshButton = new System.Windows.Forms.Button();
             this.tableLayoutPanel1.SuspendLayout();
             this.tableLayoutPanel2.SuspendLayout();
             this.panel1.SuspendLayout();
@@ -109,6 +109,18 @@
             this.panel1.Size = new System.Drawing.Size(350, 32);
             this.panel1.TabIndex = 2;
             // 
+            // portRefreshButton
+            // 
+            this.portRefreshButton.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("portRefreshButton.BackgroundImage")));
+            this.portRefreshButton.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Zoom;
+            this.portRefreshButton.Location = new System.Drawing.Point(159, 4);
+            this.portRefreshButton.Margin = new System.Windows.Forms.Padding(3, 4, 3, 4);
+            this.portRefreshButton.Name = "portRefreshButton";
+            this.portRefreshButton.Size = new System.Drawing.Size(25, 24);
+            this.portRefreshButton.TabIndex = 2;
+            this.portRefreshButton.UseVisualStyleBackColor = true;
+            this.portRefreshButton.Click += new System.EventHandler(this.portRefreshButton_Click);
+            // 
             // settingButton
             // 
             this.settingButton.Location = new System.Drawing.Point(207, 3);
@@ -191,18 +203,6 @@
             this.printText.TabIndex = 2;
             this.printText.TabStop = false;
             // 
-			// portRefreshButton
-			// 
-			this.portRefreshButton.BackgroundImage = ((System.Drawing.Image)(resources.GetObject("portRefreshButton.BackgroundImage")));
-			this.portRefreshButton.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Zoom;
-			this.portRefreshButton.Location = new System.Drawing.Point(159, 4);
-			this.portRefreshButton.Margin = new System.Windows.Forms.Padding(3, 4, 3, 4);
-			this.portRefreshButton.Name = "portRefreshButton";
-			this.portRefreshButton.Size = new System.Drawing.Size(25, 24);
-			this.portRefreshButton.TabIndex = 2;
-			this.portRefreshButton.UseVisualStyleBackColor = true;
-			this.portRefreshButton.Click += new System.EventHandler(this.portRefreshButton_Click);
-			// 
             // SerialCommApp
             // 
             this.AutoScaleDimensions = new System.Drawing.SizeF(7F, 15F);

MySolution/SerialComApp/SerialCommApp.resx

@@ -120,20 +120,20 @@
   <assembly alias="System.Drawing" name="System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
   <data name="portRefreshButton.BackgroundImage" type="System.Drawing.Bitmap, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
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 </value>
   </data>
   <data name="$this.Icon" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">