Smack, gtalk connectivity error PLAIN: not-authorized

I am trying to connect to gmail using SMACK API but getting the below error and I am stuck with this past 2 days.

Exception in thread "main" org.jivesoftware.smack.sasl.SASLErrorException: SASLError using PLAIN: not-authorized    at org.jivesoftware.smack.SASLAuthentication.authenticate(SASLAuthentication.java:348)    at org.jivesoftware.smack.tcp.XMPPTCPConnection.login(XMPPTCPConnection.java:244)    at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:442)

I am using smack 4.0.3 jars and Java 7. gmail is not blocked in my office network. I have tired all the suggestion given in the forums.

    1. setting SASLMechanism to PLAIN / DIGEST-MD5.  

    2. adding the Thread.sleep delay after connect. 

    3. by setting the dummy SSLSocketFactory.

    4. removing the domain name from user name.

Below is code which I am trying to execute.

publicclass JabberExample {    publicstaticvoid main(String[] args) throws Exception{         XMPPTCPConnection con = new XMPPTCPConnection("gmail.com");        SASLAuthentication.supportSASLMechanism("PLAIN",0);         con.connect();        con.login("username", "password");         Chat chat = ChatManager.getInstanceFor(con).createChat("chatusernam@gmail.com", new MessageListener() {             publicvoid processMessage(Chat chat, Message message) {                 System.out.println("Received message: " + message);             }         });         chat.sendMessage("Howdy!");         // Disconnect from the server         con.disconnect();    }} 

I hope i get some suggestions and help here.