In reply to sunils:
To debug this issue, go in this sequence:
1) Check Driver to Sequencer connection, probably in your agent.
2) Check Sequence body() method for start_item(req) amd finish_item(req).
3) Go to the test, and see if run_phase() calls start method on appropriate Sequencer for the Driver.
4) I am not sure about send_response(rsp) as I've never used it. If you want to communicate response back to Sequencer, use:
5) Your driver is not exactly blocking the testcase, it's the sequence you are starting is blocking execution of test run_phase(). Use displays there to debug this.