scp via java

Question

What is the best method of performing an scp transfer via the Java programming language? It seems I may be able to perform this via JSSE, JSch or the bouncy castle java libr

Answer 1

Here is an example to upload a file using JSch:

ScpUploader.java:

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.io.ByteArrayInputStream;
import java.util.Properties;

public final class ScpUploader
{
    public static ScpUploader newInstance()
    {
        return new ScpUploader();
    }

    private volatile Session session;
    private volatile ChannelSftp channel;

    private ScpUploader(){}

    public synchronized void connect(String host, int port, String username, String password) throws JSchException
    {
        JSch jsch = new JSch();

        Properties config = new Properties();
        config.put("StrictHostKeyChecking", "no");

        session = jsch.getSession(username, host, port);
        session.setPassword(password);
        session.setConfig(config);
        session.setInputStream(System.in);
        session.connect();

        channel = (ChannelSftp) session.openChannel("sftp");
        channel.connect();
    }

    public synchronized void uploadFile(String directoryPath, String fileName, byte[] fileBytes, boolean overwrite) throws SftpException
    {
        if(session == null || channel == null)
        {
            System.err.println("No open session!");
            return;
        }

        // a workaround to check if the directory exists. Otherwise, create it
        channel.cd("/");
        String[] directories = directoryPath.split("/");
        for(String directory : directories)
        {
            if(directory.length() > 0)
            {
                try
                {
                    channel.cd(directory);
                }
                catch(SftpException e)
                {
                    // swallowed exception

                    System.out.println("The directory (" + directory + ") seems to be not exist. We will try to create it.");

                    try
                    {
                        channel.mkdir(directory);
                        channel.cd(directory);
                        System.out.println("The directory (" + directory + ") is created successfully!");
                    }
                    catch(SftpException e1)
                    {
                        System.err.println("The directory (" + directory + ") is failed to be created!");
                        e1.printStackTrace();
                        return;
                    }

                }
            }
        }

        channel.put(new ByteArrayInputStream(fileBytes), directoryPath + "/" + fileName, overwrite ? ChannelSftp.OVERWRITE : ChannelSftp.RESUME);
    }

    public synchronized void disconnect()
    {
        if(session == null || channel == null)
        {
            System.err.println("No open session!");
            return;
        }

        channel.exit();
        channel.disconnect();
        session.disconnect();

        channel = null;
        session = null;
    }
}

AppEntryPoint.java:

import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.SftpException;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public final class AppEntryPoint
{
    private static final String HOST = "192.168.1.1";
    private static final int PORT = 22;
    private static final String USERNAME = "root";
    private static final String PASSWORD = "root";

    public static void main(String[] args) throws IOException
    {
        ScpUploader scpUploader = ScpUploader.newInstance();

        try
        {
            scpUploader.connect(HOST, PORT, USERNAME, PASSWORD);
        }
        catch(JSchException e)
        {
            System.err.println("Failed to connect the server!");
            e.printStackTrace();
            return;
        }

        System.out.println("Successfully connected to the server!");

        byte[] fileBytes = Files.readAllBytes(Paths.get("C:/file.zip"));

        try
        {
            scpUploader.uploadFile("/test/files", "file.zip", fileBytes, true); // if overwrite == false, it won't throw exception if the file exists
            System.out.println("Successfully uploaded the file!");
        }
        catch(SftpException e)
        {
            System.err.println("Failed to upload the file!");
            e.printStackTrace();
        }

        scpUploader.disconnect();
    }
}

Answer 2

JSch is a nice library to work with. It has quite an easy answer for your question.

JSch jsch=new JSch();
  Session session=jsch.getSession(user, host, 22);
  session.setPassword("password");


  Properties config = new Properties();
  config.put("StrictHostKeyChecking","no");
  session.setConfig(config);
  session.connect();

  boolean ptimestamp = true;

  // exec 'scp -t rfile' remotely
  String command="scp " + (ptimestamp ? "-p" :"") +" -t "+rfile;
  Channel channel=session.openChannel("exec");
  ((ChannelExec)channel).setCommand(command);

  // get I/O streams for remote scp
  OutputStream out=channel.getOutputStream();
  InputStream in=channel.getInputStream();

  channel.connect();

  if(checkAck(in)!=0){
    System.exit(0);
  }

  File _lfile = new File(lfile);

  if(ptimestamp){
    command="T "+(_lfile.lastModified()/1000)+" 0";
    // The access time should be sent here,
    // but it is not accessible with JavaAPI ;-<
    command+=(" "+(_lfile.lastModified()/1000)+" 0\n");
    out.write(command.getBytes()); out.flush();
    if(checkAck(in)!=0){
      System.exit(0);
    }
  }

You can find complete code at

http://faisalbhagat.blogspot.com/2013/09/java-uploading-file-remotely-via-scp.html

Answer 3

I wrote an scp server which is much easier than others. I use Apache MINA project (Apache SSHD) to develop it. You can take a look here: https://github.com/boomz/JSCP Also you can download the jar file from /jar directory. How to use? Take a look on: https://github.com/boomz/JSCP/blob/master/src/Main.java