The most helpful content you can provide to fix a communication issue between rtsp-simple-server and an external hardware or software, is a network dump of the data exchanged between the server and the target, that can be generated in this way:
2) Start capturing on the interface used for exchanging RTSP (if the server and the target software are both installed in your pc, the interface is probably "loopback", otherwise it's the one of your network card)
3) Start the server and replicate the issue
4) Stop capturing, save the result in .pcap format
