I have to implement chat messaging using Android SIP client but unable to find any related classes or listener. I have already implemented calling feature using SIP.
Use pjsip or Linphone opensource project.Both libraries are written using c code and well documented to build for android with sample application.
If you want pure java implementation of sip IM ,go for jainsip stack based implementation.Actually android default sip client is based on jainsip but it not support Im and only works in wifi.
Telestax implementation of jainsip helps to create apps for android.You can read this documentation for more details.Also a sample android implementation you can find here.