Thé port in SDP is the port from which the endpoint wants to receive. It is not mandatory to use the same port to send traffic. Unless you know the endpoint will use symetric rtp. There is no way to know in avance which port it will use to send. Le 12 juin 2022 14:40, hamed r <hamed.rasstegar(a)gmail.com> a écrit : hello i have problem on receive source port rtp packet client-ip = 5.202.105.250 server-ip = 194.5.205.33 client2-ip = 188.212.241.46 In the 200 ok packet from client2 ,The value 4002 is set in the audio port [image: photo_2022-06-12_17-44-37.jpg] I expect rtp packets to be sent to me from source port 4002, but these packets are sent to me from another source , which is port 55755 in the image below, and I just opened this port(4002) in the firewall. If I turn on my firewall service, all packets will be dropped. I have to have this firewall [image: photo_2022-06-12_17-44-48.jpg] thanks for help me __________________________________________________________ Kamailio - Users Mailing List - Non Commercial Discussions * sr-users(a)lists.kamailio.org Important: keep the mailing list in the recipients, do not reply only to the sender! Edit mailing list options or unsubscribe: * https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users