Running programs using JSch in the background

Question

I am trying to connect to a remote machine using JSch. All my systems are running on ubuntu including my production machines. I am able to successfully connect and run the jar file. But when i close the window the program automatically shuts down. What i'm trying to achieve now is to run this jar file in the background.

I have appended the sudo command with '&' and the server doesn't even start in this case. I have tried using a shell channel but here to the server doesn't startup or closes on stopping my program.

I've also tried the nohup and disown commands to run in the background. When i get the process state using ps ux the STAT column shows T which according to this means the process has stopped. I've been stuck here since 3 days.

1. Is there anything wrong with the code i've written? why is the server unable to run in the background?
2. setPty(true) -> what does this do?
3. is there a way to stop the password from printing to the console when i enter it?
4. I have been testing this code in my local network. while connecting to our production servers we pass a permissions file along like this: sudo ssh -i permissionFilePath serverName@ipAddress. Will i have to change my approach again for passing this permission file to gain access to production systems?

i am using the following version of JSch:

<dependency>
    <groupId>com.jcraft</groupId>
    <artifactId>jsch</artifactId>
    <version>0.1.53</version>
</dependency>

I am using the following code:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;

public class App extends Application {
    @Override
    public void start(Stage primaryStage) {
        Button btn = new Button();
        btn.setText("click");
        btn.setOnAction(new EventHandler<ActionEvent>() {
            public void handle(ActionEvent arg0) {
                try {
                    JSch objJSch = new JSch();
                    Session objSession;
                    objSession = objJSch.getSession("userName", "host");
                    objSession.setPassword("password");
                    objSession.setConfig("StrictHostKeyChecking", "no");
                    System.out.println("Establishing Connection...");
                    objSession.connect();
                    System.out.println("Connection established.");
                    Channel objChannel = objSession.openChannel("exec");
                    ((ChannelExec) objChannel).setCommand("cd {{path to my jar file}};sudo java -jar start.jar");
                    ((ChannelExec) objChannel).setErrStream(System.err);
                    ((ChannelExec) objChannel).setPty(true);//why should i use this??
                    InputStream in = objChannel.getInputStream();
                    OutputStream out = objChannel.getOutputStream();
                    objChannel.connect();
                    out.write(("password" + "\n").getBytes());
                    out.flush();
                    BufferedReader br = new BufferedReader(new InputStreamReader(in));
                    String s;
                    while ((s = br.readLine()) != null) {
                        System.out.println(s);
                    }
                    while (!objChannel.isClosed()) {
                        System.out.println("Waiting to close channel");
                    }
                    System.out.println("disconnecting...");
                    objChannel.disconnect();
                    objSession.disconnect();
                    System.out.println("disconnected.");
                } catch (JSchException e) {
                    if (e.getMessage().equalsIgnoreCase("Auth fail"))
                        System.out.println("Authorization failed...");
                    else
                        e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        StackPane root = new StackPane();
        root.getChildren().add(btn);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

Answer 1

 Your Code
((ChannelExec) objChannel).setCommand("cd {{path to my jar file}};sudo java -jar start.jar");

Modify it to :
((ChannelExec) objChannel).setCommand("cd {{path to my jar file}};sudo java -jar start.jar > /dev/null 2>&1 &");

Which will resolve your issue.