/**
   * Determines whether a vaild session exists for the contact of remote machine.
   *
   * @param sshContact ID of SSH Contact
   * @return <tt>true</tt> if the session is connected <tt>false</tt> otherwise
   */
  public boolean isSessionValid(ContactSSH sshContact) {
    Session sshSession = sshContact.getSSHSession();
    if (sshSession != null) if (sshSession.isConnected()) return true;

    // remove reference to an unconnected SSH Session, if any
    sshContact.setSSHSession(null);
    return false;
  }
  /**
   * Creates a channel for shell type in the current session channel types = shell, sftp, exec(X
   * forwarding), direct-tcpip(stream forwarding) etc
   *
   * @param sshContact ID of SSH Contact
   */
  public void createShellChannel(ContactSSH sshContact) throws IOException {
    try {
      Channel shellChannel = sshContact.getSSHSession().openChannel("shell");

      // initalizing the reader and writers of ssh contact
      sshContact.initializeShellIO(shellChannel.getInputStream(), shellChannel.getOutputStream());

      ((ChannelShell) shellChannel)
          .setPtyType(sshContact.getSSHConfigurationForm().getTerminalType());

      // initializing the shell
      shellChannel.connect(1000);

      sshContact.setShellChannel(shellChannel);

      sshContact.sendLine("export PS1=");
    } catch (JSchException ex) {
      sshContact.setSSHSession(null);
      throw new IOException("Unable to create shell channel to remote" + " server");
    }
  }
 /**
  * Closes the SSH Session associated with the contact
  *
  * @param sshContact ID of SSH Contact
  */
 void closeSSHSession(ContactSSH sshContact) {
   sshContact.getSSHSession().disconnect();
   sshContact.setSSHSession(null);
 }