Retrieve the next available UDP port from the server to stream video over RTP by making an API call

I would say Janus is really amazing! I am doing some POC and hope someone can help me.

I am sending stream to janus server over UDP/RTP as broadcaster. I was able to assign a port in the configuration for a broadcaster client, but how can I configure the server to provider next available UDP port to stream video over RTP by making an API call. Is this possible at all? If yes, can you please point me to the right document.

Thank you very much!