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 libraries. None of these solutions seem to have an easy answer.

Answer 1

This is high-level solution, no need to reinvent. Quick and dirty!

1) First, go to http://ant.apache.org/bindownload.cgi and download latest Apache Ant binary. (nowadays, apache-ant-1.9.4-bin.zip).

2) Extract the downloaded file and find the JAR ant-jsch.jar ("apache-ant-1.9.4/lib/ant-jsch.jar"). Add this JAR in your project. Also ant-launcher.jar and ant.jar.

3) Go to Jcraft jsch SouceForge Project and download the jar. Nowadays, jsch-0.1.52.jar. Also Add this JAR in your project.

Now, can you easyly use into java code the Ant Classes Scp for copy files over network or SSHExec for commands in SSH servers.

4) Code Example Scp:

// This make scp copy of 
// one local file to remote dir

org.apache.tools.ant.taskdefs.optional.ssh.Scp scp = new Scp();
int portSSH = 22;
String srvrSSH = "ssh.your.domain";
String userSSH = "anyuser"; 
String pswdSSH = new String ( jPasswordField1.getPassword() );
String localFile = "C:\\localfile.txt";
String remoteDir = "/uploads/";

scp.setPort( portSSH );
scp.setLocalFile( localFile );
scp.setTodir( userSSH + ":" + pswdSSH + "@" + srvrSSH + ":" + remoteDir );
scp.setProject( new Project() );
scp.setTrust( true );
scp.execute();

Answer 2

jsCH has worked great for me. Below is an example of a method that will connect to sftp server and download files to specified directory. It is recommended to stay away from disabling StrictHostKeyChecking. Although a little bit more difficult to set up, for security reasons specifying the known hosts should be the norm.

jsch.setKnownHosts("C:\Users\test\known_hosts"); recommended

JSch.setConfig("StrictHostKeyChecking", "no"); - not recommended

import com.jcraft.jsch.*;
 public void downloadFtp(String userName, String password, String host, int port, String path) {


        Session session = null;
        Channel channel = null;
        try {
            JSch ssh = new JSch();
            JSch.setConfig("StrictHostKeyChecking", "no");
            session = ssh.getSession(userName, host, port);
            session.setPassword(password);
            session.connect();
            channel = session.openChannel("sftp");
            channel.connect();
            ChannelSftp sftp = (ChannelSftp) channel;
            sftp.get(path, "specify path to where you want the files to be output");
        } catch (JSchException e) {
            System.out.println(userName);
            e.printStackTrace();


        } catch (SftpException e) {
            System.out.println(userName);
            e.printStackTrace();
        } finally {
            if (channel != null) {
                channel.disconnect();
            }
            if (session != null) {
                session.disconnect();
            }
        }

    }

Answer 3

plug: sshj is the only sane choice! See these examples to get started: download, upload.

Answer 4

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 5

I looked at a lot of these solutions and didn't like many of them. Mostly because the annoying step of having to identify your known hosts. That and JSCH is at a ridiculously low level relative to the scp command.

I found a library that doesn't require this but it's bundled up and used as a command line tool. https://code.google.com/p/scp-java-client/

I looked through the source code and discovered how to use it without the command line. Here's an example of uploading:

    uk.co.marcoratto.scp.SCP scp = new uk.co.marcoratto.scp.SCP(new uk.co.marcoratto.scp.listeners.SCPListenerPrintStream());
    scp.setUsername("root");
    scp.setPassword("blah");
    scp.setTrust(true);
    scp.setFromUri(file.getAbsolutePath());
    scp.setToUri("root@host:/path/on/remote");
    scp.execute();

The biggest downside is that it's not in a maven repo (that I could find). But, the ease of use is worth it to me.

Answer 6

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