How to open port 1935 on 3Proxy?

Question

proxy

Good day!
I ran into such a problem, I can’t view a webinar from workstations that are connected through a proxy, the documentation says to open port 1935 to view webinars. The firewall and antivirus were previously disabled, both on the server and on the clients, but this did not help, I checked the availability of the port using the telnet command, the port is not available, I checked the same thing via https://virtualroom.ru/service/connection/ . Naturally, everything works fine from the proxy server itself and the ports are available.