java smack + ejabberd 连接成功，登录失败，怎么解决

源码,eclipse中用java 写了个junit 测试类
 ConnectionConfiguration config = new ConnectionConfiguration("172.16.195.79",5222);
        config.setDebuggerEnabled(true);
        XMPPConnection connection = new XMPPConnection(config);
        try {
connection.connect();
log.info("connect success! "+connection.isConnected());
} catch (XMPPException e) {
log.info("connect faild!");
e.printStackTrace();
}
        try {
connection.login("ceshi", "123456");
log.info("login success!");
} catch (XMPPException e) {

log.info("login faild! "+connection.isAuthenticated());
e.printStackTrace();
}结果
INFO>  connect success! true
INFO>  login faild! false
No response from the server.: 
at org.jivesoftware.smack.SASLAuthentication.bindResourceAndEstablishSession(SASLAuthentication.java:307)
at org.jivesoftware.smack.SASLAuthentication.authenticate(SASLAuthentication.java:214)
at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:341)
at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:301)
at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:283)
at com.cn.li.xmpp.ChatTest.testw(ChatTest.java:49)