Sip Client app for android using native sip APIs

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http://stackoverflow.com – I am new to Android and got project developing sip client app for android. I am taking help from developer.android but my client is not registering to server. I wonder what mistake i have made. import android.app.Activity; import android.content.Intent; import android.net.sip.SipException; import android.net.sip.SipManager; import android.net.sip.SipProfile; import android.net.sip.SipRegistrationListener; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import java.text.ParseException; import android.app.PendingInten (HowTos)