java使用ganymed-ssh2远程连接Linux报IO异常，请帮忙看看原因

package health_checker;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;import ch.ethz.ssh2.Connection;
import ch.ethz.ssh2.Session;
import ch.ethz.ssh2.StreamGobbler;public class JaveSSH{  public static void main(String[] args)  {    String hostname = "50.130.2.3"; //要登陆目标主机    String username = "root"; //登陆用的用户名    String password = "root"; //登陆用到的密码    try    {      /* Create a connection instance */      Connection conn = new Connection(hostname);      /* Now connect */      conn.connect();      /* Authenticate */
      
      boolean isAuthenticated = conn.authenticateWithPassword(username,
          password);      if (isAuthenticated == false) {        throw new IOException("Authentication failed.");
      }      /* Create a session */      Session sess = conn.openSession();      //sess.execCommand("uname -a && date && uptime && who");      sess.execCommand("ps aux ");      System.out.println("Here is some information about the remote host:");      InputStream stdout = new StreamGobbler(sess.getStdout());      BufferedReader br = new BufferedReader(new InputStreamReader(stdout));      while (true)      {        String line = br.readLine();        if (line == null) {          break;
        }        System.out.println(line);      }      /* Show exit status, if available (otherwise "null") */      System.out.println("ExitCode: " + sess.getExitStatus());      /* Close this session */      sess.close();      /* Close the connection */      conn.close();    }    catch (IOException e)    {      e.printStackTrace(System.err);    }  }}==================================
系统报错
java.io.IOException: Password authentication failed. at ch.ethz.ssh2.auth.AuthenticationManager.authenticatePassword(AuthenticationManager.java:300) at ch.ethz.ssh2.Connection.authenticateWithPassword(Connection.java:309) at health_checker.JaveSSH.main(JaveSSH.java:43)Caused by: java.io.IOException: Authentication method password not supported by the server at this stage. at ch.ethz.ssh2.auth.AuthenticationManager.authenticatePassword(AuthenticationManager.java:270) ... 2 more