如何使用JSch访问FTP服务器？

Question

我在我的本地Windows 7机器上安装了FileZilla FTP Server.我还在同一台机器上安装了FileZilla FTP客户端.两者之间的连接成功,确认服务器和客户端伙伴关系存在.

我写了一个简单快捷的Jsch程序,用于连接FileZilla FTP服务器,下面是程序:

public class TestJSch {

/** Creates a new instance of TestCommonsNet */
public TestJSch() {
}

/**
 * main - Unit test program
 * 
 * @param args
 *            Command line arguments
 * 
 */
public static void main(String[] args) {
    try {
        String ftpHost = "127.0.0.1";
        int ftpPort = 21;// 14147;
        // int ftpPort = 990;// 14147;
        String ftpUserName = "kedar";
        String ftpPassword = "XXXXXXXXXXX";
        String ftpRemoteDirectory = "C:\\KEDAR\\Java\\FTP_Folder";
        String fileToTransmit = "C:\\KEDAR\\Java\\File_Folder\\Customer.txt";
        String identityfile = "C:\\KEDAR\\Java\\Ftp\\certificate.crt";

        //
        // First Create a JSch session
        //
        JSch.setLogger(new MyLogger());
        System.out.println("Creating session.");

        JSch jsch = new JSch();

        String knownHostsFilename = "C:\\Windows\\System32\\drivers\\etc\\hosts";
        jsch.setKnownHosts(knownHostsFilename);
        jsch.addIdentity(identityfile);
        Session session = null;
        Channel channel = null;
        ChannelSftp c = null;

        //
        // Now connect and SFTP to the SFTP Server
        //
        try {
            // Create a session sending through our username and password
            session = jsch.getSession(ftpUserName, ftpHost, ftpPort);
            System.out.println("Session created.");
            session.setPassword(ftpPassword);
            // Security.addProvider(new com.sun.crypto.provider.SunJCE());

            // b
            // Setup Strict HostKeyChecking to no so we dont get the
            // unknown host key exception
            //
            java.util.Properties config = new java.util.Properties();
            config.put("StrictHostKeyChecking", "no");
            session.setConfig(config);
            session.connect();
            System.out.println("Session connected.");

            //
            // Open the SFTP channel
            //
            System.out.println("Opening Channel.");
            channel = session.openChannel("sftp");
            channel.connect();
            c = (ChannelSftp) channel;
        } catch (Exception e) {
            System.err.println("Unable to connect to FTP server."
                    + e.toString());
            throw e;
        }

        //
        // Change to the remote directory
        //
        System.out.println("Changing to FTP remote dir: "
                + ftpRemoteDirectory);
        c.cd(ftpRemoteDirectory);

        //
        // Send the file we generated
        //
        try {
            File f = new File(fileToTransmit);
            System.out.println("Storing file as remote filename: "
                    + f.getName());
            c.put(new FileInputStream(f), f.getName());
        } catch (Exception e) {
            System.err
                    .println("Storing remote file failed." + e.toString());
            throw e;
        }   

        //
        // Disconnect from the FTP server
        //
        try {
            c.quit();
        } catch (Exception exc) {
            System.err.println("Unable to disconnect from FTPserver. "
                    + exc.toString());
        }

    } catch (Exception e) {
        System.err.println("Error: " + e.toString());
    }

    System.out.println("Process Complete.");
    System.exit(0);
}

public static class MyLogger implements com.jcraft.jsch.Logger {
    static java.util.Hashtable name = new java.util.Hashtable();
    static {
        name.put(new Integer(DEBUG), "DEBUG: ");
        name.put(new Integer(INFO), "INFO: ");
        name.put(new Integer(WARN), "WARN: ");
        name.put(new Integer(ERROR), "ERROR: ");
        name.put(new Integer(FATAL), "FATAL: ");
    }

    public boolean isEnabled(int level) {
        return true;
    }

    public void log(int level, String message) {
        System.err.print(name.get(new Integer(level)));
        System.err.println(message);
    }
}
}

我试过运行这个程序,下面是FTP日志:

(000033)9/12/2011 13:08:53 PM - (未登录)(127.0.0.1)>已连接,发送欢迎信息...
(000033)9/12/2011 13:08:53 PM - ( -尚未登录)(127.0.0.1)> 220-FileZilla Server版本0.9.39 beta
(000033)9/12/2011 13:08:53 PM - (未登录)(127.0.0.1)> 220-Tim撰写Kosse(Tim.Kosse@gmx.de)
(000033)9/12/2011 13:08:53 PM - (未登录)(127.0.0.1)> 220请访问http://sourceforge.net/projects/filezilla /
(000033)9/12/2011 13:08:53 PM - (未登录)(127.0.0.1)> SSH-2.0-JSCH-0.1.44
(000033)9/12/2011 13:08:53 PM - (未登录)(127.0.0.1)> 500语法错误,命令无法识别.
(000033)9/12/2011 13:09:54 PM - (未登录)(127.0.0.1)> 421超过登录时间.关闭控制连接.
(000033)9/12/2011 13:09:54 PM - (未登录)(127.0.0.1)>已断开连接.

我不明白为什么JSch程序发出SSH-2.0-JSCH-0.1.44命令,然后拒绝通信.我们如何避免这种情况？

Answer 1

JSch不是FTP客户端.JSch是一个SSH客户端(包含SFTP实现).

SSH协议是一种允许与服务器进行安全连接,进行shell访问,文件传输或端口转发的协议.为此,服务器必须具有SSH服务器(通常在端口22上,但可能会有所不同).SFTP是一种二进制文件传输协议,通常通过SSH进行隧道传输,与FTP无关(除了名称).

如果你想使用JSch下载/上传文件,您需要安装并激活您的计算机上的SSH/SFTP服务器(相应的你要访问的计算机).

对于FTP,您必须使用其他Java库(Apache Commons FTPClient似乎很有名,来自这里的问题).

顺便说一下,JSch 的已知主机文件是列出SSH主机公钥的文件,而不是列出其IP地址的文件(这是您尝试在此处提供的Windows配置文件).