Question

I’m trying to connect to SSH Unix server on button click (code written in actionPerformed() method). I’m using JSch for connecting to SSH server. The code is written in SwingWorker class as it is a network operation.

private void testConnectionButtonActionPerformed(java.awt.event.ActionEvent evt) {                                                     

        SwingWorker<Boolean, Void> sw = new SwingWorker<Boolean, Void>(){

            @Override
            protected Boolean doInBackground() throws Exception {
                JSch jsch = new JSch();

                String host = "ServerHost";
                String username = "username";
                String password = "password";

                Session session = jsch.getSession(username, host);
                session.setPassword(password);

                session.setTimeout(20000);
                System.out.println("Connecting to server...");
                session.connect();

                return true;
            }

            @Override
            public void done(){
                try {
                    System.out.println(get().toString());
                } catch (Exception ex) {
                    System.out.err(ex);
                } 
            }
        };

        sw.execute();

    }  

But after running the with correct host, username and password details, I get the below error all the time:

com.jcraft.jsch.JSchException: timeout: socket is not established
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
    at java.util.concurrent.FutureTask.get(FutureTask.java:83)
    at javax.swing.SwingWorker.get(SwingWorker.java:583)

But whenever I run the same code in standalone program, I mean instead for writing actionPerformed() method, If I write it in normal method and calling from main() method. It will work. when I integrate the same code with Button Click’s actionPerformed() method, it will give me above exception.

Can anyone suggest what I’m doing wrong here or any modification should be made to the code.

I tried to connect to SSH Server using “SSHJ” implementation, but I get the below error:

java.net.SocketException: Connection reset
    at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
    at java.util.concurrent.FutureTask.get(FutureTask.java:83)
    at javax.swing.SwingWorker.get(SwingWorker.java:583)

Can someone help me – how to move forward?

Answer 1

I took your code, wrapped it in some GUI code (and converted it to non-generics to be able to compile it with the same settings as the rest of the JSch examples). It works for me. Try this, and report what exception you get (it has a bit more exception logging).

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;

import com.jcraft.jsch.*;



class SwingWorkerExample {

    JTextField hostField;
    JTextField userNameField;
    JTextField passwordField;
    JPanel panel;


    public SwingWorkerExample() {
        JPanel p = panel = new JPanel(new GridLayout(0,2));
        hostField = new JTextField(20);
        userNameField = new JTextField(20);
        passwordField = new JPasswordField(20);
        JButton testButton = new JButton("connect!");
        testButton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent ev) {
                    testConnectionButtonActionPerformed(ev);
                }
            });
        p.add(new JLabel("host:"));
        p.add(hostField);
        p.add(new JLabel("user:"));
        p.add(userNameField);
        p.add(new JLabel("password:"));
        p.add(passwordField);
        p.add(testButton);
    }

    public JPanel getPanel() {
        return panel;
    }

    private void testConnectionButtonActionPerformed(ActionEvent evt) {

        SwingWorker sw = new SwingWorker(){

                protected Object doInBackground() throws Exception {
                    try {
                        JSch jsch = new JSch();

                        String host = hostField.getText();
                        String username = userNameField.getText();
                        String password = passwordField.getText();

                        Session session = jsch.getSession(username, host);
                        session.setPassword(password);
                        session.setConfig("StrictHostKeyChecking", "no");

                        session.setTimeout(20000);
                        System.out.println("Connecting to server...");
                        session.connect();

                        return session;
                    }
                    catch(Exception ex) {
                        ex.printStackTrace();
                        throw ex;
                    }
                }

                public void done(){
                    try {
                        System.out.println(get());
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    }
                }
            };

        sw.execute();

    }


    public static void main(String[] egal) {
        EventQueue.invokeLater(new Runnable(){public void run() {
            SwingWorkerExample ex = new SwingWorkerExample();
            JFrame f = new JFrame("bla");
            f.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
            f.setContentPane(ex.getPanel());
            f.pack();
            f.setVisible(true);
        }});
    }
}