I will suggest you to create a event that sends out report periodically. The pseudo code is like the followings:
if(events & SEND_RPT)
{
afSendData(DEFAULT_ENDPOINT,DEFAULT_ENDPOINT,0, TEST_CLUSTER, testMessage1, 4);
osal_start_timerEx(YourTaskId, SEND_RPT, 3);
return events ^= SEND_RPT;
}