As shown below, one of the stun server is falling
Maybe it is causing problem with iphone
[]# ./stunclient stun.zoiper.com
Binding test: success
Local address: 10.130.70.99:54619
Mapped address: 201.16.225.169:53292
[r]# ./stunclient stun.zoiper.com
Binding test: fail
[]# nslookup stun.zoiper.com
Server: 10.130.10.1
Address: 10.130.10.1#53
Non-authoritative answer:
Name: stun.zoiper.com
Address: 192.99.24.9
Name: stun.zoiper.com
Address: 185.117.83.50
[]# ./stunclient 192.99.24.9
Binding test: success
Local address: 10.130.70.99:60141
Mapped address: 201.16.225.169:53545
]# ./stunclient 185.117.83.50
Binding test: fail
