Why do I see the registration message rport = local port when I capture packets from my app?

[weidongliu]

I use a fixed sip port number in my ios app and use the udp protocol. Occasionally, a successful registration message will appear with rport = local port. Then, when someone calls in, I answer the call and reply with 200ok. I will not receive an ack until I receive an hangup in about 30 seconds. When I switch to other wifi it works fine. From my log, I've noticed this Dialog [0x8d4ad387] was not ACK'd within T1*64 seconds, it is going to be terminated.

[weidongliu]

I use linphone-sdk version 5.2.98