According to the article you posted -
The actual Real-time Transport Protocol (RTP) streams are sent using dynamically allocated UDP ports in the range of 5004 – 65535. Without a way to open these UDP ports on any firewall in the path dynamically, the streams will fail to reach their destination.

You need to open and forward those ports to your PC or put your PC in the DMZ to test the solution.

Also review the section Working With Different NAT Device Configurations.

I don't use any messaging software so I can't be of further help.