启动备用端口时，跟端口相关的值需要重新设置

lib/config/constant.dart

@@ -12,13 +12,13 @@ class Constant {
   static int localServerPort = 35982;
   static const localServerPortOption = [35982, 35983, 35984];
 
-  static final String localServerUrl = 'http://$localServerHost:$localServerPort';
+  static String localServerUrl = 'http://$localServerHost:$localServerPort';
 
-  static final String localFileUrl = 'http://127.0.0.1:$localServerPort';
+  static String localFileUrl = 'http://127.0.0.1:$localServerPort';
   static const String localServerTemp = '/temp';
-  static final String localServerTempFileUrl = '$localFileUrl$localServerTemp';
+  static String localServerTempFileUrl = '$localFileUrl$localServerTemp';
   static const String localServerTest = '/test';
-  static final String localServerTestFileUrl = '$localFileUrl$localServerTest';
+  static String localServerTestFileUrl = '$localFileUrl$localServerTest';
 
   /// obs 相关
   /// /////////////////////////////////////////////////////////////////////////////////////////////////////////////////

lib/services/local_server_service.dart

@@ -24,6 +24,12 @@ class LocalServerService {
       try {
         server = await HttpServer.bind(InternetAddress.loopbackIPv4, Constant.localServerPortOption[i]);
         Constant.localServerPort = server.port;
+        // 端口改变之后，相应改变其它关联用到端口的值
+        Constant.localServerUrl = 'http://${Constant.localServerHost}:${Constant.localServerPort}';
+        Constant.localFileUrl = 'http://127.0.0.1:${Constant.localServerPort}';
+        Constant.localServerTempFileUrl = '${Constant.localFileUrl}${Constant.localServerTemp}';
+        Constant.localServerTestFileUrl = '${Constant.localFileUrl}${Constant.localServerTest}';
+
         print('本地服务器启动在端口: ${server.port}');
         break;
       } on SocketException catch (e) {