CODEWITHSUNDEEP
javaandroidsftpjschdownload
adventuredoge
adventuredoge

Reputation: 345

Downloading file via SFTP using JSCH (android)

I'm trying to make an app that downloads a file from a server using SFTP. Whenever I run the debugger, everything seems to be fine with no errors. My log says that it has downloaded the specified file. However, I can't seem to find the file that was supposedly downloaded anywhere in my device. Any help?

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.SftpException;

import java.util.List;


public class MainActivity extends Activity {

    private String user = "user";
    private String pass = "pass";
    private String host = "hostname";
    private int portNum = 22;

    private String fileName = "sample.txt";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new AsyncTask<Void, Void, List<String>>() {
            @Override
            protected List<String> doInBackground(Void... params) {
                try {
                    Downloader(fileName);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                return null;
            }

        }.execute();
    }

    public void Downloader(String fileName) {

        JSch jsch = new JSch();
        Session session = null;

        String knownHostsDir = "/home/user/";

        try {
            jsch.setKnownHosts(knownHostsDir);
        } catch (JSchException e) {
            e.printStackTrace();
        }

        try {

            session = jsch.getSession(user, host, portNum);
            session.setConfig("StrictHostKeyChecking", "no");
            session.setPassword(pass);
            session.connect();

            Channel channel = session.openChannel("sftp");
            channel.connect();
            ChannelSftp sftpChannel = (ChannelSftp) channel;
            sftpChannel.get(fileName);

            Log.d(fileName, " has been downloaded");

            sftpChannel.exit();
            session.disconnect();

        } catch (JSchException e) {
            e.printStackTrace();
        } catch (SftpException e) {
            e.printStackTrace();
        }
    }

}

Upvotes: 0

Views: 3272

Answers (1)

Kenster
Kenster

Reputation: 25448

ChannelSftp sftpChannel = (ChannelSftp) channel;
sftpChannel.get(fileName);
Log.d(fileName, " has been downloaded");

The single-argument version of ChannelSftp.get() doesn't write the remote file to a local file. It returns an InputStream. You're supposed to read the contents of the remote file from the InputStream, like this for example:

try (FileOutputStream out = new FileOutputStream("/some/file")) {
    try (InputStream in = sftpChannel.get(fileName)) {
        // read from in, write to out
        byte[] buffer = new byte[1024];
        int len;
        while ((len = in.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
    }
}

Alternately, there are other versions of the get() method which will write the remote content to a local file for you.

Upvotes: 1

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