Only port 443 (SSL) is required to be open for communication between the Uptime Infrastructure Monitor monitoring station and vCenter and ESX servers.
This is typically the same port used when connecting to vCenter/ESX hosts via the vSphere desktop client.
All SOAP API calls are performed through this port.
Other Port related articles:
Required Ports for the Uptime Infrastructure Monitor Monitoring Station
What ports are required for WMI agentless monitoring
Add firewall rule to open port 9998 for Linux agent
Changing the Windows Agent Port
Configuring SQL Server Ports