Hub log is full with below error and Robots are not reporting ..
hub: nimSession - failed to connect session to HUBIP:48001, error code 10055
hub: nimSession - failed to connect session to HUBIP:48001, error code 10055
hub: sockConnect - connect to hubIP 48000 failed 10060
hub: nimSession - failed to connect session to hubIP:48000, error code 10060
hub: nimSession - failed to connect session to hubIP:48000, error code 10060
The possible reason is
if too many network connection open from hub side to communicate with robot , then it get stuck as ERROR CODE: 10055 is basically a network related issue .Thats why when hub restarted initially it works fine , then when all connection establish issue start occurring again.
run netstat -an|findstr "<enter filter parameter here>'' command to check how much HUB related connection establish.
Release : 9.0.2
Component : UIM - HUB
ERROR CODE :10055 is a network /system setting related issue :
As If you try to set up TCP connections from ports that are greater than 5000, the local computer responds with above code and
"An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full."
Below Microsoft KB can help to change the registry value
https://support.microsoft.com/en-us/help/196271/when-you-try-to-connect-from-tcp-ports-greater-than-5000-you-receive-t
Proper UIM sizing :
Please refer UIM sizing guide to check how much robot should report to a hub
https://techdocs.broadcom.com/us/en/ca-enterprise-software/it-operations-management/unified-infrastructure-management/9-0-2/installing/pre-installation-planning/ca-uim-sizing-recommendations.html#concept.dita_f4b87772767eef37070b35c09f690b065cb97ea4_CAUIM902SizingRecommendations