Splashtop Classroom connections require port 443 to be open, including non-https traffic.
If Splashtop Classroom sessions cannot be established within your network, please ensure the following addresses are not blocked in the network web filter:
- st2-relay.api.splashtop.com
- st2.api.splashtop.com
- *.relay.splashtop.com (including wildcard)