With plain transport? But tulpes ports dont correlate with rtsp server ports for clients
mediasoup does not implement RTSP. The control layer of RTSP may be implemented in Node.js and I assume that, other than that, RTSP uses a common RTP over UDP which can be done with PlainTransport.
However my answer is like 4 times bigger than your question and you provide zero real details. I won’t learn RTSP to answer this question so, if you wish, be much more specific.