add disconnect to server

src/main/java/ftp/sar/controller/ServerPanelController.java

@@ -48,6 +48,7 @@ public class ServerPanelController implements Initializable {
 
     @FXML
     public void closeConnection(Event e) {
+        this.server.closeConnection();
         this.mainPageController.serverContainer.getChildren().remove(this.serverPane);
     }
 

src/main/java/ftp/sar/server/Server.java

@@ -76,4 +76,15 @@ public class Server {
     public void setServerPanel(ServerPanelController serverPanelController) {
         this.serverPanelController = serverPanelController;
     }
+
+    public void closeConnection() {
+        try {
+            this.getConnector().disconnect();
+            this.socket.close();
+        } catch (CannotConnectException e) {
+            e.printStackTrace();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
 }

src/main/java/ftp/sar/server/ServerConnector.java

@@ -146,4 +146,8 @@ public class ServerConnector {
             e.printStackTrace();
         }
     }
+
+    public void disconnect() throws CannotConnectException {
+        this.sendRequest("DISCONNECT");
+    }
 }