SIP call in Android

I'm using NGN stack library for SIP calls

If I test on the local server when connecting Wi-Fi, it can work normally whether audio or video. However, on the original server, I can't make a call even if the server fails to hit the request. If I use other applications, such as "zoiper", it can work normally

The following error occurs when you click the call button after registering two clients. The following is the logcat output of the error

12-14 10:35:54.146: D/org.doubango.ngn.services.impl.NgnSipService(4383): OnDialogEvent (Transport error,3)
12-14 10:35:54.146: D/org.doubango.ngn.sip.NgnAVSession(4383): setState(TERMINATED)
12-14 10:35:54.147: D/dalvikvm(4383): create interp thread : stack size=128KB
12-14 10:35:54.149: D/org.doubango.ngn.media.NgnProxyAudioProducer(4383): stopCallback

please help me out.

resolvent:

Yes, I found that the solution is the NAT problem. Just write the code of use stun for SIP by writing this code during configuration settings

ngnConfigService.putBoolean(
                NgnConfigurationEntry.NATT_USE_STUN_FOR_SIP, true, true);

Everything is normal now