Simple SSH connect with JSch

Question

I am trying to make something from this simple example :

SSH, execute remote commands with Android

I just want to see if I can connect from my android phone

Answer 1

A Kotlin solution:

import android.os.AsyncTask
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import com.jcraft.jsch.ChannelExec
import com.jcraft.jsch.JSch
import java.io.ByteArrayOutputStream
import java.util.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        SshTask().execute()
    }

    class SshTask : AsyncTask<Void, Void, String>() {
        override fun doInBackground(vararg p0: Void?): String {
            val output = executeRemoteCommand("demo", "password", "test.rebex.net")
            print(output)
            return output
        }
    }
}

fun executeRemoteCommand(username: String,
                         password: String,
                         hostname: String,
                         port: Int = 22): String {
    val jsch = JSch()
    val session = jsch.getSession(username, hostname, port)
    session.setPassword(password)

    // Avoid asking for key confirmation.
    val properties = Properties()
    properties.put("StrictHostKeyChecking", "no")
    session.setConfig(properties)

    session.connect()

    // Create SSH Channel.
    val sshChannel = session.openChannel("exec") as ChannelExec
    val outputStream = ByteArrayOutputStream()
    sshChannel.outputStream = outputStream

    // Execute command.
    sshChannel.setCommand("ls")
    sshChannel.connect()

    // Sleep needed in order to wait long enough to get result back.
    Thread.sleep(1_000)
    sshChannel.disconnect()

    session.disconnect()

    return outputStream.toString()
}

In build.gradle add:

dependencies {
    ...
    compile group: 'com.jcraft', name: 'jsch', version: '0.1.54'
}

Answer 2

chubbsondubs's solution is perfect. I just want to share the code that I made for this problem too for people who want a quick solution:

public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    new AsyncTask<Integer, Void, Void>(){
       @Override
       protected Void doInBackground(Integer... params) {
           try {
                 executeRemoteCommand("root", "myPW","192.168.0.26", 22);
           } catch (Exception e) {
                 e.printStackTrace();
           }
           return null;
       }
    }.execute(1);
}

public static String executeRemoteCommand(String username,String password,String hostname,int port)
        throws Exception {
    JSch jsch = new JSch();
    Session session = jsch.getSession(username, hostname, port);
    session.setPassword(password);

    // Avoid asking for key confirmation
    Properties prop = new Properties();
    prop.put("StrictHostKeyChecking", "no");
    session.setConfig(prop);

    session.connect();

    // SSH Channel
    ChannelExec channelssh = (ChannelExec)
            session.openChannel("exec");
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    channelssh.setOutputStream(baos);

    // Execute command
    channelssh.setCommand("lsusb > /home/pi/test.txt");
    channelssh.connect();
    channelssh.disconnect();

    return baos.toString();
}

Answer 3

You have to execute that code in another thread so you don't hang the UI thread is what that exception means. If the UI thread is executing a network call it can't repaint the UI so your users sees a frozen UI that doesn't respond to them while the app is waiting on the network call to finish. Android wants to avoid bad user experiences like this so it prevents you from doing things like this by throwing this exception.

Your onCreate() method should invoke another thread (I'd suggest using an AsyncTask over a raw thread) to perform the SSH connection. Then when it's done it can post the results back to the UI thread and safely update your application's UI from the UI thread.

http://developer.android.com/reference/android/os/AsyncTask.html