使用filezilla工作正常，但是当我使用FtpWebRequest时，会发生此错误，并且无法连接到远程服务器＆＃34;

Question

在以下情况下会发生此错误：

   public void UploadFile()
    {
        try
        {
            var fileName = "myFile";
            var ftpFilePath = "ftp://xxx.xxx.xxx/myfolder/";
            WebRequest.DefaultWebProxy = new WebProxy();
            var ftpRequest = WebRequest.Create(requestUri) as FtpWebRequest;
            ftpRequest.Credentials = new NetworkCredential("user", "password");
            ftpRequest.Method = method;
            ftpRequest.KeepAlive = false;
            ftpRequest.UseBinary = false;
            ftpRequest.UsePassive = false;
            ftpRequest.EnableSsl = true;
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(OnValidateCertificate);
                var requestStream = ftpRequest.GetRequestStream();
                var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);

            byte[] buffer = new byte[1024];
            while (true)
            {
                int readSize = fileStream.Read(buffer, 0, buffer.Length);
                if (readSize == 0)
                {
                    break;
                }
                requestStream.Write(buffer, 0, readSize);
            }
            fileStream.Close();
            requestStream.Close();
        }
        catch (Exception exception)
        {
            //...
        }
    }

当我在localhost和本地网络上使用FTP时，它运行良好。 但是当我尝试使用公共IP地址连接到服务器时。 发生此错误。当我使用filezilla连接到具有公共IP地址的服务器时，它没问题。请帮帮我!!