Hi, I would like to report a bug in pjsip-apps/src/python/samples/registration.py: There is a race-condition when waiting for the registration to finish. The reason is, that the semaphore is created in wait, which may be too late. Demo: add "time.sleep(2)" between acc.set_callback(acc_cb) and acc_cb.wait(): ... try: ... acc_cb = MyAccountCallback(acc) acc.set_callback(acc_cb) time.sleep(2) acc_cb.wait() ... Solution: Create the semaphore before, e.g. in MyAccountCallback.__init__. I've attached a patch. thanks, Roland