I am using openser with mediaproxy enabled. All device behind NAT can make/receive call without problem. However, when an end device connect to the openser directly using public IP (without NAT), the following problem will occur. -when make outgoing calls, I can hear the receiver but receiver can't hear me -when incoming call, it works as normal Does modiaproxy can handle device using NAT and without NAT? How can I solve the above problem? Is it the port setting problem? Below is the dial plan and the ini file of mediaproxy. http://meerkat.no-ip.com/openser/openser.txt http://meerkat.no-ip.com/openser/mediaproxy.txt Thanks, unplug