C# 实现FTP客户端的小例子

本文是利用C# 实现FTP客户端的小例子，主要实现上传，下载，删除等功能，以供学习分享使用。

思路：

• 通过读取FTP站点的目录信息，列出对应的文件及文件夹。
• 双击目录，则显示子目录，如果是文件，则点击右键，进行下载和删除操作。
• 通过读取本地电脑的目录，以树状结构展示，选择本地文件，右键进行上传操作。
  

涉及知识点：

• FtpWebRequest【实现文件传输协议 (FTP) 客户端】 / FtpWebResponse【封装文件传输协议 (FTP) 服务器对请求的响应】Ftp的操作主要集中在两个类中。
• FlowLayoutPanel  【流布局面板】表示一个沿水平或垂直方向动态排放其内容的面板。
• ContextMenuStrip 【快捷菜单】 主要用于右键菜单。
• 资源文件：Resources 用于存放图片及其他资源。
  

效果图如下

左边：双击文件夹进入子目录，点击工具栏按钮‘上级目录'返回。文件点击右键进行操作。

右边：文件夹则点击前面+号展开。文件则点击右键进行上传。

核心代码如下

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace FtpClient
{
 public class FtpHelper
 {
  #region 属性与构造函数

  /// <summary>
  /// IP地址
  /// </summary>
  public string IpAddr { get; set; }

  /// <summary>
  /// 相对路径
  /// </summary>
  public string RelatePath { get; set; }

  /// <summary>
  /// 端口号
  /// </summary>
  public string Port { get; set; }

  /// <summary>
  /// 用户名
  /// </summary>
  public string UserName { get; set; }

  /// <summary>
  /// 密码
  /// </summary>
  public string Password { get; set; }



  public FtpHelper() {

  }

  public FtpHelper(string ipAddr, string port, string userName, string password) {
   this.IpAddr = ipAddr;
   this.Port = port;
   this.UserName = userName;
   this.Password = password;
  }

  #endregion

  #region 方法


  /// <summary>
  /// 下载文件
  /// </summary>
  /// <param name="filePath"></param>
  /// <param name="isOk"></param>
  public void DownLoad(string filePath, out bool isOk) {
   string method = WebRequestMethods.Ftp.DownloadFile;
   var statusCode = FtpStatusCode.DataAlreadyOpen;
   FtpWebResponse response = callFtp(method);
   ReadByBytes(filePath, response, statusCode, out isOk);
  }

  public void UpLoad(string file,out bool isOk)
  {
   isOk = false;
   FileInfo fi = new FileInfo(file);
   FileStream fs = fi.OpenRead();
   long length = fs.Length;
   string uri = string.Format("ftp://{0}:{1}{2}", this.IpAddr, this.Port, this.RelatePath);
   FtpWebRequest request = (FtpWebRequest)WebRequest.Create(uri);
   request.Credentials = new NetworkCredential(UserName, Password);
   request.Method = WebRequestMethods.Ftp.UploadFile;
   request.UseBinary = true;
   request.ContentLength = length;
   request.Timeout = 10 * 1000;
   try
   {
    Stream stream = request.GetRequestStream();

    int BufferLength = 2048; //2K
    byte[] b = new byte[BufferLength];
    int i;
    while ((i = fs.Read(b, 0, BufferLength)) > 0)
    {
     stream.Write(b, 0, i);
    }
    stream.Close();
    stream.Dispose();
    isOk = true;
   }
   catch (Exception ex)
   {
    Console.WriteLine(ex.ToString());
   }
   finally {
    if (request != null)
    {
     request.Abort();
     request = null;
    }
   }
  }

  /// <summary>
  /// 删除文件
  /// </summary>
  /// <param name="isOk"></param>
  /// <returns></returns>
  public string[] DeleteFile(out bool isOk) {
   string method = WebRequestMethods.Ftp.DeleteFile;
   var statusCode = FtpStatusCode.FileActionOK;
   FtpWebResponse response = callFtp(method);
   return ReadByLine(response, statusCode, out isOk);
  }

  /// <summary>
  /// 展示目录
  /// </summary>
  public string[] ListDirectory(out bool isOk)
  {
   string method = WebRequestMethods.Ftp.ListDirectoryDetails;
   var statusCode = FtpStatusCode.DataAlreadyOpen;
   FtpWebResponse response= callFtp(method);
   return ReadByLine(response, statusCode, out isOk);
  }

  /// <summary>
  /// 设置上级目录
  /// </summary>
  public void SetPrePath()
  {
   string relatePath = this.RelatePath;
   if (string.IsNullOrEmpty(relatePath) || relatePath.LastIndexOf("/") == 0 )
   {
    relatePath = "";
   }
   else {
    relatePath = relatePath.Substring(0, relatePath.LastIndexOf("/"));
   }
   this.RelatePath = relatePath;
  }

  #endregion

  #region 私有方法

  /// <summary>
  /// 调用Ftp,将命令发往Ftp并返回信息
  /// </summary>
  /// <param name="method">要发往Ftp的命令</param>
  /// <returns></returns>
  private FtpWebResponse callFtp(string method)
  {
   string uri = string.Format("ftp://{0}:{1}{2}", this.IpAddr, this.Port, this.RelatePath);
   FtpWebRequest request; request = (FtpWebRequest)FtpWebRequest.Create(uri);
   request.UseBinary = true;
   request.UsePassive = true;
   request.Credentials = new NetworkCredential(UserName, Password);
   request.KeepAlive = false;
   request.Method = method;
   FtpWebResponse response = (FtpWebResponse)request.GetResponse();
   return response;
  }

  /// <summary>
  /// 按行读取
  /// </summary>
  /// <param name="response"></param>
  /// <param name="statusCode"></param>
  /// <param name="isOk"></param>
  /// <returns></returns>
  private string[] ReadByLine(FtpWebResponse response, FtpStatusCode statusCode,out bool isOk) {
   List<string> lstAccpet = new List<string>();
   int i = 0;
   while (true)
   {
    if (response.StatusCode == statusCode)
    {
     using (StreamReader sr = new StreamReader(response.GetResponseStream()))
     {
      string line = sr.ReadLine();
      while (!string.IsNullOrEmpty(line))
      {
       lstAccpet.Add(line);
       line = sr.ReadLine();
      }
     }
     isOk = true;
     break;
    }
    i++;
    if (i > 10)
    {
     isOk = false;
     break;
    }
    Thread.Sleep(200);
   }
   response.Close();
   return lstAccpet.ToArray();
  }

  private void ReadByBytes(string filePath,FtpWebResponse response, FtpStatusCode statusCode, out bool isOk)
  {
   isOk = false;
   int i = 0;
   while (true)

   {
    if (response.StatusCode == statusCode)
    {
     long length = response.ContentLength;
     int bufferSize = 2048;
     int readCount;
     byte[] buffer = new byte[bufferSize];
     using (FileStream outputStream = new FileStream(filePath, FileMode.Create))
     {

      using (Stream ftpStream = response.GetResponseStream())
      {
       readCount = ftpStream.Read(buffer, 0, bufferSize);
       while (readCount > 0)
       {
        outputStream.Write(buffer, 0, readCount);
        readCount = ftpStream.Read(buffer, 0, bufferSize);
       }
      }
     }
     break;
    }
    i++;
    if (i > 10)
    {
     isOk = false;
     break;
    }
    Thread.Sleep(200);
   }
   response.Close();
  }
  #endregion
 }

 /// <summary>
 /// Ftp内容类型枚举
 /// </summary>
 public enum FtpContentType
 {
  undefined = 0,
  file = 1,
  folder = 2
 }
}

FTP服务端和客户端示意图

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