SSH Using Java

Overview

This article will demonstrate how using the SSH API in SSH Factory for Java you can develop a console based interactive SSH shell.

Code Example            

Download SshExample.java (2.7K)    

001 /*
002  * @(#)SshExample.java
003  *
004  * Copyright (c) JSCAPE LLC.
005  *
006  * This software is the confidential and proprietary information of
007  * JSCAPE. ("Confidential Information").  You shall not disclose such
008  * Confidential Information and shall use it only in accordance with
009  * the terms of the license agreement you entered into with JSCAPE.
010  */
011 import com.jscape.inet.ssh.*;
012 import com.jscape.inet.ssh.util.SshParameters;
013 import java.io.*;
014
015 public class SshExample implements SshListener {
016  
017  // state of SSH connection
018  private boolean connected = false;
019
020  /**
021  * Creates a new SshExample instance.
022  *
023  */
024  public SshExample() {
025  String hostname = null;
026  String username = null;
027  String password = null;
028  Ssh ssh = null;   
029
030  try {
031  BufferedReader bin =
032  new BufferedReader(new InputStreamReader(System.in));
033  System.out.print("Enter SSH hostname: ");
034  hostname = bin.readLine();
035
036  System.out.print("Enter SSH username: ");
037  username = bin.readLine();
038
039  System.out.print("Enter SSH password: ");
040  password = bin.readLine();
041
042  // create new Ssh instance
043  SshParameters sshParams = new SshParameters(hostname,username,password);
044  ssh = new Ssh(sshParams);
045  
046  // register to capture events
047  ssh.addSshListener(this);
048  
049  System.out.println("Connecting please wait...");
050  
051  // connect
052  ssh.connect();
053
054  // get output stream for writing data to SSH server
055  OutputStream out = ssh.getOutputStream();
056
057  // holds line entered at console
058  String line = null;
059
060  // read data from console
061  while (connected && (line = bin.readLine()) != null) {
062  // send line with LF to SSH server
063  line += "\n";
064  try {
065  out.write(line.getBytes());
066  out.flush();
067  } catch(Exception ioe){
068  connected = false;
069  } 
070  }      
071  } catch (Exception e) {
072  e.printStackTrace();      
073  } finally {
074  try {
075  if(connected) {
076  ssh.disconnect(); 
077  }
078  } catch(Exception e) {
079  
080  }      
081  }
082  }
083
084  /**
085  * Captures SshConnectedEvent
086  */
087  public void connected(SshConnectedEvent ev) {
088  System.out.println("Connected: " + ev.getHost());
089  connected = true;
090  }
091
092  /**
093  * Captures SshDataReceivedEvent
094  */
095  public void dataReceived(SshDataReceivedEvent ev) {
096  // send data received to console
097  System.out.print(ev.getData());
098  }
099
100  /**
101  * Captures SshDisconnectedEvent
102  */
103  public void disconnected(SshDisconnectedEvent ev) {
104  System.out.println("Disconnected: " + ev.getHost() + ". Press Enter to exit");
105  connected = false;
106  }
107
108  /**
109  * Main method for SshExample
110  * @param args
111  */
112  public static void main(String[] args) {
113  SshExample test = new SshExample();
114  }
115
116 }

1. Lines 11-13. Add necessary import statements.
2. Lines 25-27. Instance variables for SSH hostname, SSH username and SSH password.
3. Line 28. An Ssh instance for communicating with SSH server.
4. Lines 31-32. Creates a BufferedReader for obtaining SSH login information from user. BufferedReader will also be used to read data from console and submit to SSH server.
5. Lines 33-40. Obtain SSH login information from user.
6. Line 43. Create new Ssh instance, passing SSH hostname, username and password as arguments to constructor.
7. Line 46. Register to capture SSH related events.
8. Line 52. Establish connection with SSH server using SSH hostname, username and password provided in constructor.
9. Line 55. Get OutputStream to send data to SSH server.
10. Lines 58-70. Read data entered from console and send to SSH server.
11. Lines 95-98. Captures data received from SSH server and prints to console.

Comments

[nanoj]

Is there a way you can you just pass in the username and hostname and leave out the password ..
if already authenticated .

[Van]

"Is there a way you can you just pass in the username and hostname and leave out the password ..if already authenticated ."

I don't think this is possible. How is it the server would know that the client is already authenticated. Each SSH session requires authentication to occur. You cannot tie authentication for one session to an already authenticated session.