opcserver 5500 conn error to DA subscr Controller

Hi,
I am using 800xa 6.0.3.2 system . In controller log file I am getting some opcserver 5500 connection error to DA subscr controller and OPCServer 6500 conn error to AE subscr controller where one of the four controller IP is mentioned. the session log and controller settings snap shot is attached.
kindly let me know what is the reason behind this and how to resolve the same.