/// <summary>
        /// 实例化一个交互连接
        /// </summary>
        /// <param name="ip"></param>
        /// <param name="port"></param>
        /// <param name="pwd"></param>
        public Session(string ip, int port, string pwd)
        {
            _client = new ssr.Client(new Host(), ip, port);
            _cache  = new Dictionary <string, string>();

            // 执行登录
            _client.Sendln("PWD");
            _client.Sendln($"${pwd.Length}");
            _client.Send(pwd, (string data) => {
                // 判断是否成功
                if (data.StartsWith("-"))
                {
                    throw new Exception(data.Substring(1));
                }
            });
        }
 /// <summary>
 /// 释放资源
 /// </summary>
 public void Dispose()
 {
     _cache.Clear();
     _client.Dispose();
     _client = null;
 }