Add reconnect mechanism.

lib/chessapp/chess_app.dart

@@ -56,7 +56,15 @@ class ChessApp extends StatelessWidget {
             ),
           ),
         ),
+        floatingActionButton: const FloatingActionButton(
+          onPressed: reconnect,
+          child: Icon(Icons.connect_without_contact),
+        ),
       ),
     );
   }
 }
+
+void reconnect() {
+  ServerConnection.getInstance().reconnect();
+}

lib/connection/ws_connection.dart

@@ -7,6 +7,7 @@ class ServerConnection {
   static final ServerConnection _instance = ServerConnection._internal();
 
   ServerConnection._internal() {
+    print("ServerConnection._interal constructor is called");
     channel = WebSocketChannel.connect(
       Uri.parse('ws://localhost:8080'),
     );
@@ -21,7 +22,11 @@ class ServerConnection {
   }
 
   void send(String message) {
-    channel.sink.add('$message: $counter');
+    channel.sink.add('$counter $message');
     counter++;
   }
+
+  void reconnect() {
+    channel = WebSocketChannel.connect(Uri.parse('ws://localhost:8080'));
+  }
 }