This issue occurs when all ports are being exhausted on an ESXi host that is connected to the vCenter Server Appliance due to connections not being closed after use by third-party products or APIs. vCenter Server remains running though communication to the affected ESXi hosts are degraded.
to resolve this issue, the management agents are required to be restarted on the affected ESXi host
Is it the http connection between the ESXi host and the vcenter that is adding up to 500? Is there some way I can check this?
No , this is not the same, see each plugin you have on your vcsa create sessions , each running thread in side creates a session with your vcenter , even if it is not doing anything, it periodically do the garbage collection and thus create connections, each login, each operation all creates sessions. There is a way to increase the number of sessions,( I dont recall how though)
What i did was i turned off unused plugins, and disabled unwanted services on vCSA
and increased number of sessions. as said i dont recall how to do it .
it was either in vpxd.conf --> vclient.maxConnectionCount>100</maxConnectionCount // this is to increase number of concurrent connections to vCenter
Webclient.properties in vsphere-client directory on vCSA // This limits number of Web Client sessions
or combination of those