Java ftp实现文件的上传和下载ftp,sftp sun.net.ftp.FtpProtocolException:Welcome message: SSH-2.0-OpenSSH_5.1

Java ftp实现文件的上传和下载

ftp,sftp

运行后发现很长时间没有反应，很久以后抛出如下异常：sun.net.ftp.FtpProtocolException:Welcome message: SSH-2.0-OpenSSH_5.1

 

但是在cmd中ftp是可以通过的，用SecureCRT也是可以连接的，查看SecureCRT配置，看到端口是22.

 

用jdk自带包实现代码如下：

publicclass FtpTest {

 

    private FtpClientftpclient;

 

    publicvoid connectServer(String ip,int port, String username,

            String password, String path) {

        try {

            if (null == ip) {

                thrownew Exception("The service's ip is null!");

            }

            ftpclient =new FtpClient();

            //当端口号为0时，采用默认端口号

            if(port == 0){

                ftpclient.openServer(ip);

            }else{

                ftpclient.openServer(ip, port);

            }         

            //ftpclient = new FtpClient(ip, port);      

            System.out.println(ftpclient.getFtpProxyPort());

            ftpclient.login(username, password);

            System.out.println("12324");

            ftpclient.binary();

            if (null != path) {

                ftpclient.cd(path);// 跳转到服务器的指定目录

            }

        } catch (Exception e) {

            e.printStackTrace();

        }

    }  

    publicvoid connectServer(String ip, String username,

            String password, String path){

        connectServer(ip,0,username,password,path);

    }

    publicvoid closeServer() {

        if (null !=ftpclient) {

            try {

                ftpclient.closeServer();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

    }

    publicvoid ftpupload(String localfilanme, String remotefilename) {

        FileInputStream input =null;

        TelnetOutputStream out =null;

        try {

            if (null == localfilanme ||null == remotefilename) {

                thrownew Exception("文件名为空！");

            }

            File localfile =new File(localfilanme);

            if (!localfile.exists() || !localfile.isFile()

                    || !localfile.canRead()) {

                thrownew Exception("文件不存在或者不是文件！");

            }

            input =new FileInputStream(localfile);

            out =ftpclient.put(remotefilename);

            int c = 0;

            byte[] bye =newbyte[1024];

            while ((c = input.read(bye)) != -1) {

                out.write(bye, 0, c);

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            try {

                if (null != input) {

                    input.close();

                }

                if (null != out) {

                    out.close();

                }

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

    }

    publicvoid ftpdownload(String localfilename, String remotefilename) {

        FileOutputStream out =null;

        TelnetInputStream input =null;

        try {

            if (null == localfilename ||null == remotefilename) {

                thrownew Exception("文件名为空！");

            }

            File localfile =new File(localfilename);

            out =new FileOutputStream(localfile);

            input =ftpclient.get(remotefilename);

            int c = 0;

            byte[] bye =newbyte[1024];

            while ((c = input.read(bye)) != -1) {

                out.write(bye, 0, c);

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            try {

                if (null != input) {

                    input.close();

                }

                if (null != out) {

                    out.close();

                }

            } catch (IOException e) {

                e.printStackTrace();

            }

 

        }

    }

    publicstaticvoid main(String[] args) {

        FtpTest test =new FtpTest();

        String ip ="xxx";

        String username ="admin";

        String password ="admin";

        String path ="/usr/admin/test";

        test.connectServer(ip,22,username, password, path);

        System.out.println(test.ftpclient.getFtpProxyPort());

        test.ftpupload("C:\\Users\\admin\\Desktop\\123.txt","123.txt");

        test.ftpdownload("D:\\124.txt", "123.txt");

        test.closeServer();

    }

}

 

网上找了很久，没找到什么资料。通过查询ftp资料发，有这样一句解释：FTP服务一般运行在20和21两个端口。端口20用于传输控制流，而端口21用于在客户端和服务器之间传输数据流。再看SecureCRT，发现有一个sftp标签页配置，查询sftp资料，解释如下：sftp是Secure File Transfer Protocol的缩写，安全文件传送协议。可以为传输文件提供一种安全的加密方法。sftp 与 ftp 有着几乎一样的语法和功能。SFTP 为 SSH的一部份，是一种传输档案至 Blogger 伺服器的安全方式。其实在SSH软件包中，已经包含了一个叫作SFTP(Secure File Transfer Protocol)的安全文件传输子系统，SFTP本身没有单独的守护进程，它必须使用sshd守护进程（端口号默认是22）来完成相应的连接操作，所以从某种意义上来说，SFTP并不像一个服务器程序，而更像是一个客户端程序。SFTP同样是使用加密传输认证信息和传输的数据，所以，使用SFTP是非常安全的。但是，由于这种传输方式使用了加密/解密技术，所以传输效率比普通的FTP要低得多，如果您对网络安全性要求更高时，可以使用SFTP代替FTP。发现端口22是 sftp的默认端口，所以，将代码中的端口22改成21即可解决这个问题。

在http://www.dexcoder.com/selfly/article/4028中，页讲解了用jsch包sftp的方式解决。