How to forward ports correctly?

Question

Network administration

Good day!
There is a subject 2 Chinese unidentified video cameras, whose TP does not respond.
The network works through a budget TP-Link (If it comes in handy, there is OpenWRT on it).
Forwarded the ports, the web interface of the cameras comes from the Internet, but there is no image. I found the reason, the problem is that Flash Player is used for display, and through dev. browser utilities saw that this player uses, in addition to the port specified in the settings, also port 1935, which I cannot configure in the web interface. I forwarded port 1935 through Virtual Server to the IP of one camera, now everything works. And what about the second one? I can't set the same port to another IP, I can't change this port in the webcam's face. Is there any solution to the problem? I already wanted to save the camera settings and find and change the port through the HEX editor, but the config simply cannot be saved =( There is no such item. Is it possible to redirect from my external IP: 123456 to internal IP1: 1935 and IP :1234567 to internal IP2:1935.

Answer 1

one camera in forwarding the second in dmz, although as far as I saw Chinese cameras they use 81 or 82 ports and everything
can be screenshots of camera settings

Answer 2

1) I had TP-Link and there was an opportunity to forward an external port different from the internal one.
2) If this is not possible, then custom firmware will definitely help.