Hi! My application is developed in C#; Visual Studio .Net (Compact Framework 2,0) using my own wrapper DLL. I tested with success unicast and multicast calls using streamutil.c example. I developped a presence/sync server (with a custom protocol) to permit only one client to transmit at same time in same multicast channel. Now I need to create a multicast rtp channel (A kind of Push to talk application) where a client talk (pressing the PTT button) and others receive, but when the first release PTT it will be able to receive from same multicast address. Have I to destroy transmit stream and recreate a receive stream, or there is a better solution to change direction? thanks in advance Carmine -- Carmine Ruffino [MSN: cmcrew (at) tiscalinet (dot) it] [Skype ID: cmcsynth]