anchor.diff:    } else {
       request.response
         ..writeln('not exit')
  -      ..close();//没猜对的话回复false
  +      ..close();//该同学不存在的话显示not exit
     }
     if (selectinfo == '1004li') {
       request.response
  
positive.code:   } else {
      request.response
        ..writeln('not exit')
        ..close();//没猜对的话回复false
    }
    if (selectinfo == '1003qing') {
      request.response
  
negative.code:       'server susscefullly get the post data from client is: "${content}');
  }
  ///教师可根据学生的姓名学号，进行选择，从而知道学生的具体成绩信息
  void searchRequest(HttpRequest request){
    try {//try是什么意思？
      if (request.method == 'GET') {
        handleSearch(request);//42
  