LocalTunneling.java

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package edu.rice.cs.hpc.remote.tunnel;

import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.UserInfo;

/***************************************************
 * 
 * Wrapper for SSH L-Tunneling with Jsch
 *
 ***************************************************/
public class LocalTunneling 
{

    final private JSch  jsch;
    final private UserInfo userInfo;
    
    private Session session;
    private int port;
    
    private String session_id = null;
    
    public LocalTunneling(UserInfo userInfo)
    {
        jsch          = new JSch();
        this.userInfo = userInfo;
    }
    
    /*******
     * Build SSH port local forwarding connection 
     * 
     * @param login_user : username at login host
     * @param login_host : the login host
     * @param remote_host : the remote host where a server listens
     * @param port : the port number (the same as the port that
     *               the server listens)
     * 
     * @return the assigned port
     * 
     * @throws JSchException
     */
    public int connect(String login_user, String login_host, 
            String remote_host, int port)
            throws JSchException
    {
        String id = getSessionID(login_user, login_host, remote_host, port);

        if (session_id != null) {
            // check whether this connection is the same as the previous one
            if (id.equals(session_id)) {
                return this.port;
            }
        }
        session = jsch.getSession(login_user, login_host, 22);
        session.setUserInfo(userInfo);
        session.connect();
        
        int assigned_port = session.setPortForwardingL(port, remote_host, port);
        this.port = assigned_port;

        session_id = id;
        return this.port;
    }
    
    
    private String getSessionID(String login_user, String login_host, 
            String remote_host, int port)
    {
        return login_user + "@" + login_host + ":" + remote_host + ":" + port;
    }
    
    /*******
     * disconnect tunneling
     * 
     * @throws JSchException
     */
    public void disconnect() throws JSchException
    {
        session.delPortForwardingL(port);
        session.disconnect();
    }
    
    
    /*
     * (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString()
    {
        return session_id;
    }
    
    /*******
     * unit test 
     * @param args
     */
    public static void main(final String []args)
    {
        if (args.length != 4)
        {
            System.out.println("Required arguments: user password login_host remote_host");
            return;
        }
        LocalTunneling tunnel = new LocalTunneling( new UserInfo() {

            @Override
            public boolean promptPassword(String message) {
                System.out.println(message);
                return true;
            }

            @Override
            public String getPassword() {
                return args[1];
            }

            @Override
            public boolean promptPassphrase(String message) {
                System.out.println(message);
                return true;
            }

            @Override
            public String getPassphrase() {
                return null;
            }

            @Override
            public boolean promptYesNo(String message) {
                System.out.println(message);
                return true;
            }

            @Override
            public void showMessage(String message) {
                System.out.println(message);                
            }
            
        });
        
        try {
            int port = tunnel.connect(args[0], args[2], args[3], 21590 );
            System.out.println("Assigned port: " + port);
            
            tunnel.disconnect();
            
        } catch (JSchException e) {
            e.printStackTrace();
        }
    }
}