Hi, I know that pjsip is asyn manner. When both client end call, the program crash, it is because of inv_session is NULL. Here is the case 1. When other ends call, they send us BYE. We receive that BYE, release dlg->pool, hence release inv->pool 2. At exact the same time, we end call, too. We call pjsua_call_hangup. In this routine, we still reference inv_session (which is NULL because of 1), which cause crash !!! It also causes crash in the opposite direction: We end call, then receive BYE at the same time How to fix this ? -- Khoa Pham HCMC University of Science Faculty of Information Technology -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20130417/b4bfbb38/attachment-0001.html>