Hey, Ion! I try to thinking about this problem. Anyway correct written application is working ok and from the other side the "system" solution like removing file of mutex from /dev/shm directory works too :-) But at the current moment I'm very interesting in adding of more features to shared_message_queue class. As I understood this queue supplies only one client-server connection. So one message can be received only one time despite of many processes that want to read it. It seems to have internal client number counter will be a good idea. Second feature I want to ask you it add more service methods - like to get number of messages in queue (useful for profiling applications at hard data traffic). Best Regards, Dmitry Smirnov Saint-Petersburg, Russia