C# 实现的FTP服务端和客户端无法连接

 // 创建FTP连接

        private FtpWebRequest CreateFtpWebRequest(string uri, string requestMethod)

        {

            FtpWebRequest request = (FtpWebRequest)FtpWebRequest.Create(uri);

            request.Credentials = networkCredential;//获取或设置用于与 FTP 服务器通信的凭据。 

            request.KeepAlive = true;

            request.UseBinary = true;

            request.Method = requestMethod;

            return request;

        }



        // 获取服务器返回的响应体

        private FtpWebResponse GetFtpResponse(FtpWebRequest request)

        {

            FtpWebResponse response = null;

            try

            {

                response = (FtpWebResponse)request.GetResponse();//检索包含从 FTP 服务器上发送的响应数据的流

                lstbxFtpState.Items.Add("验证完毕，服务器回应信息：[" + response.WelcomeMessage + "]");

                lstbxFtpState.Items.Add("正在连接：[ " + response.BannerMessage + "]");

                lstbxFtpState.TopIndex = lstbxFtpState.Items.Count - 1;

                return response;

            }

            catch(WebException ex)

            {

                lstbxFtpState.Items.Add("发送错误。返回信息为：" + ex.Status);

                lstbxFtpState.TopIndex = lstbxFtpState.Items.Count - 1;

                return null;

            }

        }