I am working in VoIP provider and I am testing Zoiper 5 on GNU/Linux ( Ubuntu 16.04 LTS ).
I have problems with audio only on one way.
When I inspect de packets involved in the call I can see that PBX and Softphone negociate ports but Zoiper send media packets from other port . If I don't mark the option "Open random port above 3200" in "Advanced/Network/RTP Options" the softphone uses allways port 8000, in otherwise over the 3200 port but allways diferent port that negociates the PBX ( asterisk 11 ) and Zoiper 5 ( both on the same LAN ) .
With older version 3.3.25608 we don't have any problem.
Images:
Invite
200 OK
Media
Call flow sequence
IP PBX : 10.12.4.2
IP Softphone : 10.12.4.201
If I activate the debug log option in Zoiper Softphone I can see the same.
$ tail -f ./.Zoiper5/logfile_2017-12-14_*| grep -e 'rtp_port_manager' -e 'm=audio'
DEBUG | 20171214-125942.428 | RESIP:APP | 140658601230848 | rtp_port_manager.cpp:78 | Available port: 55682
m=audio 36262 RTP/AVP 8 101
m=audio 36262 RTP/AVP 8 101
m=audio 36262 RTP/AVP 8 101
m=audio 36262 RTP/AVP 8 101
m=audio 12696 RTP/AVP 8 101
m=audio 12696 RTP/AVP 8 101
m=audio 12696 RTP/AVP 8 101
DEBUG | 20171214-125945.929 | RESIP:APP | 140658601230848 | rtp_port_manager.cpp:84 | Releasing port: 55682
The module rtp_port_manager.cpp choose a port to send media ( port 55682 ) , but in sip trafic I can watch that offers other ( port 36262 ) . Finally the Softphone uses port 55682 to send media and this media is descarted by my PBX .