从FTP服务器端下载PCD点云文件到本地文件夹

　　关于从ftp服务器下载文件到本地文件夹的操作，具体代码如下：

        /// <summary>
        /// 从服务器下载PCD点云文件到本地
        /// </summary>
        public void DownloadPCDFile()
        {
            //登入到ftp的账号
            string ftpUserName = "administrator";
            //登入到ftp的密码
            string ftpUserPwd = "beris.ZDH";
            //下载后的文件存放路径
            string downloadUrl = "D:\\PointClouds";
            //需要下载的文件名
            string fileName = "materialPile_downsample.pcd";
            //需要现在的文件在ftp上的完整路径
            string fileUploadPath = "ftp://192.168.2.43/LatestPCLFile";
            Uri uri = new Uri(fileUploadPath + "/" + fileName);
            //下载后存放的路径
            string FileName = Path.GetFullPath(downloadUrl) + Path.DirectorySeparatorChar.ToString() + Path.GetFileName(uri.LocalPath);

            //创建文件流
            FileStream fs = null;
            Stream responseStream = null;
            try
            {
                //创建一个与FTP服务器联系的FtpWebRequest对象
                FtpWebRequest request = (FtpWebRequest)WebRequest.Create(uri);
                //设置请求的方法是FTP文件下载
                request.Method = WebRequestMethods.Ftp.DownloadFile;
                //连接登录FTP服务器
                request.Credentials = new NetworkCredential(ftpUserName, ftpUserPwd);
                //获取一个请求响应对象
                FtpWebResponse response = (FtpWebResponse)request.GetResponse();
                //获取请求的响应流
                responseStream = response.GetResponseStream();
                //判断本地文件是否存在，如果存在，则打开和重写本地文件
                if (File.Exists(FileName))
                {
                    fs = File.Open(FileName, FileMode.Open, FileAccess.ReadWrite);
                }
                else
                {
                    fs = File.Create(FileName);
                }

                if (fs != null)
                {
                    int buffer_count = 65536;
                    byte[] buffer = new byte[buffer_count];
                    int size = 0;
                    while ((size = responseStream.Read(buffer, 0, buffer_count)) > 0)
                    {
                        fs.Write(buffer, 0, size);
                    }
                    fs.Flush();
                    fs.Close();
                    responseStream.Close();
                }
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();
                }
                if (responseStream != null)
                {
                    responseStream.Close();
                }
            }
        }