ArcGIS Monitor uses specific ports to communicate with other machines. The ports you need to allow on your firewall are described below.
HTTPS port 30443
Monitor only communicates through port 30443 by default. Ensure that your firewall allows communication through this port. Your users can access Monitor through this port.
HTTP port 30080
By default, Monitor supports HTTPS communication only, and communication through port 30080 is not allowed. Administrators can change this setting in Monitor to allow HTTP plaintext communication through port 30080, but this is a less secure option.
Firewalls between Monitor machines
Firewalls may exist between Monitor Server and Monitor Agent machines that are located in different network environments. When Monitor Agent is registered to Monitor Server, Monitor Agent sends a request to Monitor Server to open a WebSocket connection for bidirectional communication. Depending on your firewall settings, you may need to adjust inbound rules for Monitor Server and outbound rules for Monitor Agent.