Set udpsink source (sender) port in pipeline [NAT traversal]

[Vassiliev]

Hi all,
I need to send video pipeline from Server to a Client which is under symmetric NAT. So I need to 'punch a hole' in the NAT. For that reason I send UDP packet from the Client's port XXX to the Server's port YYY. Server gets packet from the Client's ZZZ port and then starts sending video pipeline using udpsink to this ZZZ port. But for it to work, pipeline's UDP source port should be YYY for NAT traversal while, as I found, it is randomly choosing.
So my question is how to set this udpsink source port on exact port? (I am writing in Python if it means)

Thanks in advance.

[Vassiliev]

I've found the solution: just need to use bind-port=port