About the problem that video conferencing cannot be performed with three terminals

I’d appreciate it if you could answer the following questions.
I am not good at English but I appreciate your cooperation.

Terminal A and terminal B are communicable.(No firewall)
Terminal B and Terminal C cannot communicate.(There is a firewall)
Terminal C and Terminal A are communicable.(There is a firewall)

If C joins while A and B are in a video conference, the video conference will be disabled.
If C leaves the video conference, the video conference will come back.

I think that if you have a video conferencing with three terminals, the video conferencing is possible because the communication is done through Jitsi server.

If terminals can’t communicate with each other, can’t I video conference?

Hi there and welcome to our community!

Even if there is a firewall between terminals, we would fallback using the conference server to exchange audio / video.

Are you running these tests on your own Jitsi server or on meet.jit.si ?

Thank you for your quick response.
I see.
I use my own Jitsi server.

Then check the JVB and Jicofo logs, in addition to the JS console. You are probably going to see ICE failures. Make sure your terminals are able to connect to the server, via UDP.

Does the problem occur if the terminal cannot access the Jitsi server via UDP?

Yes

Unfortunately, I cannot see the logs right away because of the customer environment. Currently trying to check.

Which ports need to be open for UDP access from the device to the Jitsi server?

At present, Jitsi server opens INPUT 10000 / udp in firewalld configuration.

Port 10000 UDP should do, assuming that’s how you configured the JVB.